[SCSI] mpt2sas : release diagnotic buffers prior host reset

Diagnostic buffer support is already there in the driver.  This support allows
applications to pull ring buffers from controller firmware for debugging
firmware related issues.

What this patch does is sends reqeust to firmware to release the buffers prior
to host reset.   This will allow what ever debug info is there prior to reset
to be dma'd to host memory. With out this fix, some of the debug data would
been lost.

Signed-off-by: Eric Moore <eric.moore@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>