ext4: include missing blk.h

If missing, lbaint_t typedef will not be found in some cases.

[The proper fix for the commit above at the time would have been to
 include ide.h as only since commit 1a73661bc7 ("dm: Add a new header
 for block devices") is the typedef in blk.h]

Fixes: 04735e9c55 ("Fix ext2/ext4 filesystem accesses beyond 2TiB")
Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>

include/ext_common.h

@@ -20,6 +20,7 @@
 #ifndef __EXT_COMMON__
 #define __EXT_COMMON__
 
+#include <blk.h>
 #include <compiler.h>
 
 struct cmd_tbl;