Merge pull request #1366 from antonio-nino-diaz-arm/an/ignore-spdx

checkpatch: Ignore SPDX_LICENSE_TAG

.checkpatch.conf

@@ -36,6 +36,10 @@
 # This is not Linux so don't expect a Linux tree!
 --no-tree
 
+# The Linux kernel expects the SPDX license tag in the first line of each file.
+# We don't follow this in the Trusted Firmware.
+--ignore SPDX_LICENSE_TAG
+
 # This clarifes the lines indications in the report.
 #
 # E.g.: