mpt3sas: fix Kconfig dependency problem for mpt2sas back compatibility

The non-PCI builds of the O day test project are failing:

On Thu, 2015-12-03 at 05:02 +0800, kbuild test robot wrote:
> warning: (SCSI_MPT2SAS) selects SCSI_MPT3SAS which has unmet direct
> dependencies (SCSI_LOWLEVEL && PCI && SCSI)

The problem is that select and depend don't interact because Kconfig doesn't
have a SAT solver, so depend picks up dependencies and select does onward
selects, but select doesn't pick up dependencies.  To fix this, we need to add
the correct dependencies to the MPT2SAS option like this.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Fixes: b840c362
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>