ahci: imx: Add imx53 SATA temperature sensor support

Add a hwmon entry to get the temperature from the die of imx53
SATA.

The original patch was made by Richard Zhu for kernel 2.6.x:
ENGR00134041-MX53-Add-the-SATA-AHCI-temperature-monitor.patch

Signed-off-by: Fabien Lahoudere <fabien.lahoudere@collabora.co.uk>
Signed-off-by: Tejun Heo <tj@kernel.org>