[SCSI] megaraid_sas: Use lowest memory bar for SR-IOV VF support

The following patch modifies the megaraid_sas driver to select the
lowest memory bar available so the driver will work in SR-IOV VF
environments where the memory bar mapping changes.

Signed-off-by: Adam Radford <aradford@gmail.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>