src/include: Add space after comma

Fix the following error detected by checkpatch.pl:

ERROR: space required after that ',' (ctx:VxV)

TEST=Build and run on Galileo Gen2

Change-Id: I297bfc3d03dc95b471d3bb4b13803e81963841b5
Signed-off-by: Lee Leahy <Leroy.P.Leahy@intel.com>
Reviewed-on: https://review.coreboot.org/18647
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

src/include/stdlib.h

@@ -3,8 +3,8 @@
 
 #include <stddef.h>
 
-#define min(a,b) MIN((a),(b))
-#define max(a,b) MAX((a),(b))
+#define min(a, b) MIN((a), (b))
+#define max(a, b) MAX((a), (b))
 
 void *memalign(size_t boundary, size_t size);
 void *malloc(size_t size);