basic/missing: move BLKGETDISKSEQ to missing_fs.h

As it is defined at linux/fs.h.

src/basic/missing_loop.h

@@ -1,7 +1,6 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 #pragma once
 
-#include <linux/fs.h>
 #include <linux/loop.h>
 
 #ifndef LOOP_CONFIGURE
@@ -15,10 +14,6 @@ struct loop_config {
 #define LOOP_CONFIGURE 0x4C0A
 #endif
 
-#ifndef BLKGETDISKSEQ
-#define BLKGETDISKSEQ _IOR(0x12,128,__u64)
-#endif
-
 #ifndef LOOP_SET_STATUS_SETTABLE_FLAGS
 #define LOOP_SET_STATUS_SETTABLE_FLAGS (LO_FLAGS_AUTOCLEAR | LO_FLAGS_PARTSCAN)
 #endif