This patch adds a call to sbc_check_prot() within sbc_setup_write_same()
code to perform the various protection releated sanity checks, including
failing if WRPROTECT or RDPROTECT is set for a backend device that has
not advertised support for T10-PI.

Also, since WRITE_SAME + T10-PI is currently not supported by IBLOCK +
FILEIO backends, go ahead and fail if ->execute_write_same() is invoked
with a non zero cmd->prot_op.

Cc: Martin Petersen <martin.petersen@oracle.com>
Cc: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>