[SCSI] mpt fusion: kill warnings in mptbase.h on parisc64

Verified all the arches necessary select the CONFIG_64BIT symbol. This
also kills the warning (since it was using the 32-bit case) on parisc64
and mips64.

Signed-off-by: Kyle McMartin <kyle@mcmartin.ca>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>