scsi: sg: Consolidate compat ioctl handling

Merge the native and compat ioctl handlers into a single one using
in_compat_syscall().

Link: https://lore.kernel.org/r/20210724072033.1284840-6-hch@lst.de


Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>