[SCSI] mptfusion - fix panic in mptsas_slave_configure

Driver panic when RAID logical volume was present when driver
loaded, or when a RAID logical volume was created on the fly.

This issue was created in due to recent scsi_transport_sas change,
when sas_read_port_mode_page was added into the mptsas drivers
slave_config entry point.

This new API expects that all sdev's to be assocated to an rphy, however
that is not the case for logical volumes, as they are created using
scsi_add_device, instead of sas_rphy_add().

Signed-off-by: Eric Moore <Eric.Moore@lsil.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>