[SCSI] scsi_dh_alua: Fix Erroneous TPG ID check

For Target Portal Group IDs occupying the full 2 bytes in the
RTPG response, the following group_id check in the alua_rtpg
routine always fails in scsi_dh_alua.c:

if (h->group_id == (ucp[2] << 8) + ucp[3]) {

This causes the ALUA handler to wrongly identify the AAS of
a specified device as well as incorrectly interpreting the
supported AAS of the target as seen by the following entries
in the /var/log/messages:

"alua: port group 3ea state A supports tousna"
"alua: port group 3e9 state A supports tousna"

This is because 'ucp' is wrongly declared in alua_rtpg as
a character pointer instead of an unsigned character pointer.

Signed-off-by: Martin George <marting@netapp.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>