[SCSI] mpt2sas: Add Extended Type for Diagnostic Buffer support

Added tests for registry entries of EXBuffSize, EXImmed, and EXType to
support the new Extended diag buffer type.  Modified code where necessary to
handle the new ExtendedType field in the F/W diagnostic Post and Release
messages.

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