[SCSI] mpt2sas: User resource_size_t instead of unsigned long

Use resource_size_t to define the type resource for the system interface
register set.
The existing implementation was using "unsigned long" which would be 32 bit
in 32 bit OS.  If 32 bit OS is using 64 bit physical
address space for the system interface register set, we need to shift to
using resource_size_t which takes care of physical address space.

Signed-off-by: Kashyap Desai <kashyap.desai@lsi.com>
Reviewed-by: Eric Moore <eric.moore@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>