common: Drop part.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/block/blk_legacy.c b/drivers/block/blk_legacy.c
index 0c343f7..e3ee778 100644
--- a/drivers/block/blk_legacy.c
+++ b/drivers/block/blk_legacy.c
@@ -5,6 +5,8 @@
  */
 
 #include <common.h>
+#include <blk.h>
+#include <part.h>
 #include <linux/err.h>
 
 struct blk_driver *blk_driver_lookup_type(int if_type)