arm: omap: reset sata on boot

On OMAP platforms (like OMAP5) Linux kernel fails to detect a SATA
device if it is used by U-Boot.

It happens because U-Boot does not reset SATA controller before boot.

Reset the controller on OS boot so that Linux will have a clean state
to work with.

Signed-off-by: Dmitry Lifshitz <lifshitz@compulab.co.il>
Reviewed-by: Tom Rini <trini@ti.com>