scsi: aacraid: fix a signedness bug

The problem is that ->reset_state is a u8 but it can be set to -1 or -2 in
aac_tmf_callback() and the error handling in aac_eh_target_reset() relies
on it to be signed.

[mkp: fixed typo]

Fixes: 0d643ff3 ("scsi: aacraid: use aac_tmf_callback for reset fib")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>