[SCSI] mptfusion: Added new less expensive RESET (Message Unit Reset)

Message Unit Reset - instructs the IOC to reset the Reply Post and
Free FIFO's. All the Message Frames on Reply Free FIFO are
discarded. All posted buffers are freed, and event notification is
turned off.  IOC doesnt reply to any outstanding request. This will
transfer IOC to READY state.  Message unit ready is less expensive
operations than Hard Reset.  soft reset will not force Firmware to
reload again, it only do clean up of Message units.

mpt_Soft_Hard_ResetHandler will first try for Soft Reset,if
it fails then go for big hammer reset which is Hard Reset.

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