[SCSI] megaraid_{mm,mbox}: 64-bit DMA capability fix

It is known that 2 LSI Logic MegaRAID SATA RAID Controllers (150-4 and
150-6) don't support 64-bit DMA. Unfortunately currently this check is
wrong and driver sets 64-bit DMA mode for these devices.

Signed-off-by: Andrey Mirkin <amirkin@sw.ru>
Acked-by: "Ju, Seokmann" <Seokmann.Ju@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>