[SCSI] mpt2sas: Added SCSIIO, Internal and high priority memory pools to support multiple TM

1) create a pool of high priority message frames in the region of memory
between message frames and chains.  The modifications are in
_base_allocate_memory_pools.  Also create a seperate pool of memory for
internal commands located near the same region of memory.  The pool of high
priority message frames is restriced by the facts->HighPriorityCredit.

2) Create additional API for accessing request message frames. New function
mpt2sas_base_get_smid_hpr is for highpriority request. New function
mpt2sas_base_get_smid_scsiio for SCSI_IO, passing in the scsi command
pointer.  The mpt2sas_base_get_smid function is for requesting internal
commands.

3) Added new function _base_get_cb_idx to obtain the callback
index from one of the three pools of request message frames.

4) Removed wrapper functions _scsih_scsi_lookup_set and
_scsih_scsi_lookup_getclear. These were removed because this handling was
moved into mpt2sas_base_get_smid_scsiio and mpt2sas_base_free_smid.

5) The function mpt2sas_base_free_smid is modified so the request message
frames are put back on one of the three pools of request message frames.

Signed-off-by: Kashyap Desai <kashyap.desai@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>