scsi: introduce scsi_sense_from_errno()

The new function is an extension of the switch statement in scsi-disk.c
which also includes the errno cases only found in sg_io_sense_from_errno.
This allows us to consolidate the errno handling.

Extracted from a patch by Hannes Reinecke <hare@suse.de>.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>