[POWERPC] sata_fsl: reduce compatibility to fsl,pq-sata

as prescribed in Documentation/powerpc/booting-without-of.txt.

Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Acked-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>