[SCSI] mptfusion: Corrected declaration of device_missing_delay

device missing delay is 8 bit value in io unit pg1. Making correct variable
declaration for device_missing_delay.

The driver is storing the calculated device missing delay in IOC structure
as a u8 instead of a u16. It needs to be a u16 if the delay is > 255.

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