docs/user-guide.md: Renamed legacy `FVP_TSP_RAM_LOCATION`

`FVP_TSP_RAM_LOCATION` has been renamed into `ARM_TSP_RAM_LOCATION`.

docs/user-guide.md

@@ -973,7 +973,7 @@ sections.
     `-C cluster<X>.cpu<X>.RVBAR=@<base-address-of-bl31>`, to the new value of
     `BL31_BASE`.
 
-9.  Changing the default value of `FVP_TSP_RAM_LOCATION` will also require
+9.  Changing the default value of `ARM_TSP_RAM_LOCATION` will also require
     changing the value of
     `--data="<path-to><bl32-binary>"@<base-address-of-bl32>` to the new value of
     `BL32_BASE`.