imx-common: sata: return failure if not i.MX6DQPlus

The i.MX6DQPlus support sata interface, we should not
return failure when CPU is i.MX6DQPlus.

Signed-off-by: Peng Fan <van.freenix@gmail.com>
Cc: Stefano Babic <sbabic@denx.de>