Clarify "Getting the TF source code" in user guide

Remove the following redundant sentence from the user guide, which
implies the user should use the TF version from the Linaro release,
which was not the intention:

"However, the rest of this document assumes that you got the
Trusted Firmware as part of the Linaro release."

Also, tidied up the grammar in this section.

Change-Id: I5dae0b68d3683e2a85a7b3c6a31222182a66f6c8

docs/user-guide.md

@@ -57,47 +57,43 @@ optional tools may be needed:
 4.  Getting the Trusted Firmware source code
 --------------------------------------------
 
-The Trusted Firmware source code can be obtained as part of the standard Linaro
-releases, which provide a full software stack, including the Trusted Firmware,
-normal world firmware, Linux kernel and device tree, file system as well as any
-additional micro-controller firmware required by the platform. This version of
-Trusted Firmware is tested with the [Linaro 15.10 Release][Linaro Release Notes].
+The Trusted Firmware (TF) source code can be obtained as part of the standard
+Linaro releases, which provide a full software stack, including TF, normal
+world firmware, Linux kernel and device tree, file system as well as any
+additional micro-controller firmware required by the platform. This TF version
+is tested with the [Linaro 15.10 Release][Linaro Release Notes].
 
-Note 1: Both the LSK kernel or the latest tracking kernel can be used with the
-ARM Trusted Firmware, choose the one that best suits your needs.
+Note 1: Both the LSK kernel or the latest tracking kernel can be used with TF;
+choose the one that best suits your needs.
 
 Note 2: Currently to run the latest tracking kernel on FVP with GICv3 driver,
 some modifications are required to UEFI. Refer
 [here](#11--changes-required-for-booting-linux-on-fvp-in-gicv3-mode)
 for more details.
 
-The Trusted Firmware source code can then be found in the `arm-tf/` directory.
-This is the full git repository cloned from Github. The revision checked out by
-the `repo` tool is indicated by the manifest file. Depending on the manifest
-file you're using, this might not be the latest development version. To
-synchronize your copy of the repository and get the latest updates, use the
-following commands:
+The TF source code will then be in `arm-tf/`. This is the upstream git
+repository cloned from GitHub. The revision checked out by the `repo` tool is
+indicated by the manifest file. Depending on the manifest file you're using,
+this might not be the latest upstream version. To synchronize your copy of the
+repository and get the latest updates, use the following commands:
 
     # Change to the Trusted Firmware directory.
     cd arm-tf
 
-    # Download the latest code from Github.
+    # Download the latest code from GitHub.
     git fetch github
 
     # Update your working copy to the latest master.
     # This command will create a local branch master that tracks the remote
-    # branch master from Github.
+    # branch master from GitHub.
     git checkout --track github/master
 
 
-Alternatively, the Trusted Firmware source code can be fetched on its own
-from GitHub:
+Alternatively, the TF source code can be separately cloned from the upstream
+GitHub repository:
 
     git clone https://github.com/ARM-software/arm-trusted-firmware.git
 
-However, the rest of this document assumes that you got the Trusted Firmware
-as part of the Linaro release.
-
 
 5.  Building the Trusted Firmware
 ---------------------------------