ahci: st: Invoke AHCI Platform Suspend/Resume

This is where we disable IRQs on suspend and update the internal
power state during suspend/resume.

Suggested-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Tejun Heo <tj@kernel.org>