scsi: sd: Remove obsolete variable in sd_remove()

scsi: sd: Remove obsolete variable in sd_remove()

Commit 996e509bbc95 ("sd: use __register_blkdev to avoid a modprobe for an
unregistered dev_t") removed blk_register_region(devt, ...) in sd_remove()
and since then, devt is unused in sd_remove().

Hence, make W=1 warns:

  drivers/scsi/sd.c:3516:8:
      warning: variable 'devt' set but not used [-Wunused-but-set-variable]

Simply remove this obsolete variable.

[mkp: fixed commit sha]

Link: https://lore.kernel.org/r/20201214095424.12479-1-lukas.bulwahn@gmail.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>