Update MEM_SUPPORT_64BIT_DATA to be always defined

Define this macro always so we don't need the preprocessor to check it.
Convert the users to #if instead of #ifdef.

Note that '#if MEM_SUPPORT_64BIT_DATA' does not give an error if the
macro is not define. It just assumes zero.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stefan Roese <sr@denx.de>

include/compiler.h

@@ -145,7 +145,9 @@ typedef unsigned long int uintptr_t;
 #define unlikely(x)	__builtin_expect(!!(x), 0)
 
 #ifdef __LP64__
-#define MEM_SUPPORT_64BIT_DATA
+#define MEM_SUPPORT_64BIT_DATA	1
+#else
+#define MEM_SUPPORT_64BIT_DATA	0
 #endif
 
 #endif