megaraid_sas: Task management support

This patch adds task management for SCSI commands. Added functions are
task abort and target reset.

1. Currently, megaraid_sas driver performs controller reset when any IO
times out.  With task management support added, task abort and target
reset will be tried to recover timed out IO. If task management fails,
then controller reset will be performaned. If the task management
request times out, fail the request and escalate to the next
level (controller reset).

2. mr_device_priv_data will be allocated for all generations of
controller, but is_tm_capable flag will never be set for
controllers (prior to Invader series) as firmware support is not
available for task management.

3. Task management capable firmware will set is_tm_capable flag in
firmware API.

Signed-off-by: Sumit Saxena <sumit.saxena@avagotech.com>
Signed-off-by: Kashyap Desai <kashyap.desai@avagotech.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>