[SCSI] mptfusion: Set max sector count module parameter

The max_sector setting is currently hard-coded in the driver to 8192
sectors (4MB transfers). Using new module parameter, if max_sectors is
specified at load time, the default of 8192 will be overridden.

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