malloc_simple: calloc: don't call memset if malloc failed

malloc_simple() can return 0 if out of memory. Don't call memset
from calloc() in this case but rely on the caller checking
the return value.

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Reviewed-by: Marek Vasut <marex@denx.de>

common/malloc_simple.c

@@ -57,7 +57,8 @@ void *calloc(size_t nmemb, size_t elem_size)
 	void *ptr;
 
 	ptr = malloc(size);
-	memset(ptr, '\0', size);
+	if (ptr)
+		memset(ptr, '\0', size);
 
 	return ptr;
 }