[SCSI] qla4xxx: Perform context resets in case of context failures.

For 4032, context reset was the same as chip reset, and any firmware
issue was recovered by performing a chip reset.
For 82xx, the iSCSI firmware runs along with FCoE and the NIC
firmware contexts, and an error encountered doesnot essentially mean
that a chip reset is necessary.

Perform Chip resets only in the following cases:
1. Mailbox system error.
2. Mailbox command timeout.
3. fw_heartbeat_counter counter stops incrementing.

For all other cases, only perform a context reset.
1. Command Completion with an invalid srb.
2. Other mailbox failures.

Signed-off-by: Vikas Chaudhary <vikas.chaudhary@qlogic.com>
Signed-off-by: Shyam Sunder <shyam.sunder@qlogic.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>