scsi: target: Enable READ CAPACITY for PR EARO

SBC-4, Table 13 allows READ CAPACITY for all PR types.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Link: https://lore.kernel.org/r/ad095388dbc550c5b199a1dfa71bcbfc575a7abe.1701272679.git.bcodding@redhat.com


Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>