cbfs: 64-bit cleanups

cbfs used u32 in a number of cases where uintptr_t was
correct. This change builds for both 64-bit and 32-bit
boards.

Change-Id: If42c722a8a9e8d565d3827f65ed6c2cb8e90ba60
Signed-off-by: Ronald G. Minnich <rminnich@google.com>
Reviewed-on: http://review.coreboot.org/4037
Tested-by: build bot (Jenkins)
Reviewed-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-by: Aaron Durbin <adurbin@google.com>

src/lib/cbmem.c

@@ -200,7 +200,7 @@ void *cbmem_add(u32 id, u64 size)
 	cbmem_toc[0].base += size;
 	cbmem_toc[0].size -= size;
 
-	return (void *)(u32)cbmem_toc[i].base;
+	return (void *)(uintptr_t)cbmem_toc[i].base;
 }
 
 void *cbmem_find(u32 id)