scsi: isci: Use correctly sized target buffer for memcpy()

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memcpy(), avoid intentionally writing across
neighboring array fields.

Switch from rsp_ui to resp_buf, since resp_ui isn't SSP_RESP_IU_MAX_SIZE
bytes in length. This avoids future compile-time warnings.

Link: https://lore.kernel.org/r/20210528181337.792268-4-keescook@chromium.org


Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>