[SCSI] mpt fusion: Optimized SendEvent notification Using Doorbell instead FIFO

SendEventNotification was handled through FIFO, now it is using doorbell to
communicate with hardware. Added Sleep Flag as an extra argument to support
Can-Sleep feature.  Resending patch including compilation error fix reviewed
by Grant Grundler.

Signed-off-by: Kashyap Desai <kadesai@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>