Add 32 bit version of plat_get_syscnt_freq

Added plat_get_syscnt_freq2, which is a 32 bit variant of the 64 bit
plat_get_syscnt_freq. The old one has been flagged as deprecated.
Common code has been updated to use this new version. Porting guide
has been updated.

Change-Id: I9e913544926c418970972bfe7d81ee88b4da837e
diff --git a/docs/porting-guide.md b/docs/porting-guide.md
index 5004d30..0cd3613 100644
--- a/docs/porting-guide.md
+++ b/docs/porting-guide.md
@@ -1529,10 +1529,10 @@
 (that was copied during `bl31_early_platform_setup()`) if the image exists. It
 should return NULL otherwise.
 
-### Function : plat_get_syscnt_freq() [mandatory]
+### Function : plat_get_syscnt_freq2() [mandatory]
 
     Argument : void
-    Return   : uint64_t
+    Return   : unsigned int
 
 This function is used by the architecture setup code to retrieve the counter
 frequency for the CPU's generic timer.  This value will be programmed into the