common: Drop log.h from common header

Move this header out of the common header.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/membuff.c b/lib/membuff.c
index 45dae2d..36dc43a 100644
--- a/lib/membuff.c
+++ b/lib/membuff.c
@@ -8,6 +8,7 @@
 
 #include <common.h>
 #include <errno.h>
+#include <log.h>
 #include <malloc.h>
 #include "membuff.h"