scsi: esp: make cmdbuf big enough for maximum CDB size

scsi: esp: make cmdbuf big enough for maximum CDB size

While doing DMA read into ESP command buffer 's->cmdbuf', it could
write past the 's->cmdbuf' area, if it was transferring more than 16
bytes.  Increase the command buffer size to 32, which is maximum when
's->do_cmd' is set, and add a check on 'len' to avoid OOB access.

Reported-by: Li Qiang <liqiang6-s@360.cn>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 926cde5f3e4d2504ed161ed0cb771ac7cad6fd11)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>