dm integrity: remove set but not used variables

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/md/dm-integrity.c: In function 'integrity_metadata':
drivers/md/dm-integrity.c:1557:12: warning:
variable 'save_metadata_offset' set but not used [-Wunused-but-set-variable]
drivers/md/dm-integrity.c:1556:12: warning:
variable 'save_metadata_block' set but not used [-Wunused-but-set-variable]

They are never used, so remove it.

Reported-by: Hulk Robot <[e-mail]>
Signed-off-by: YueHaibing <[e-mail]>
Signed-off-by: Mike Snitzer <[e-mail]>

drivers/md/dm-integrity.c

···
 		char checksums_onstack[max((size_t)HASH_MAX_DIGESTSIZE, MAX_TAG_SIZE)];
 		sector_t sector;
 		unsigned sectors_to_process;
-		sector_t save_metadata_block;
-		unsigned save_metadata_offset;
 
 		if (unlikely(ic->mode == 'R'))
 			goto skip_io;
···
 			goto skip_io;
 		}
 
-		save_metadata_block = dio->metadata_block;
-		save_metadata_offset = dio->metadata_offset;
 		sector = dio->range.logical_sector;
 		sectors_to_process = dio->range.n_sectors;