Miscellaneous AMD F14 warning fixes

This commit adds in some more fixes to AMD F14 compile
warnings.  The change in the mtrr.c file is in prep-
aration for changes yet to com, but it is currently
innocuous.

Change-Id: I6b204fe0af16a97d982f46f0dfeaccc4b8eb883e
Signed-off-by: Frank Vibrans <frank.vibrans@amd.com>
Signed-off-by: efdesign98 <efdesign98@gmail.com>
Reviewed-on: http://review.coreboot.org/133
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
diff --git a/src/include/cpu/amd/mtrr.h b/src/include/cpu/amd/mtrr.h
index c0d6b51..3637dd9 100644
--- a/src/include/cpu/amd/mtrr.h
+++ b/src/include/cpu/amd/mtrr.h
@@ -27,8 +27,12 @@
 
 #define TOP_MEM_MSR			0xC001001A
 #define TOP_MEM2_MSR			0xC001001D
-#define TOP_MEM				TOP_MEM_MSR
-#define TOP_MEM2			TOP_MEM2_MSR
+#ifndef TOP_MEM
+  #define TOP_MEM			TOP_MEM_MSR
+#endif
+#ifndef TOP_MEM2
+  #define TOP_MEM2			TOP_MEM2_MSR
+#endif
 
 #define TOP_MEM_MASK			0x007fffff
 #define TOP_MEM_MASK_KB			(TOP_MEM_MASK >> 10)