common: Drop linux/bug.h from common header

Move this uncommon header out of the common header.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 2b7de6c..97e88b7 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -28,6 +28,7 @@
 #include <linux/gfp.h>
 #include <linux/slab.h>
 #else
+#include <linux/bug.h>
 #include <linux/err.h>
 #include <ubi_uboot.h>
 #endif