[SCSI] fusion - fix pci express bug

The fix is to write  'MPI_HIM_DIM' to the Host Interrupt Mask
register, when enabling interrupts.  Instead of the
tilde of MPI_HIM_RIM.

Apparently writing '1's to some of the reserved bits was causing
all the bits to go to `1`, which effectly disabled all interrupts.

Signed-off-by: Eric Moore <Eric.Moore@lsil.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>