ahci: imx: setup power saving methods

In order to save power consumption as much as possible.

* Disable sata phy internal pll reference clock when sysetem enter
  into suspend mode, enable it after resume.

* Setup module parameter used to enable imx ahci test power down
  mode(PDDQ) or not, when there is no device detected on the port

* minor modifications:
  - The format of the copyright is changed, because that the original
    one can't pass fsl internal patch reivew without the character
    '(c)'.
  - Exports ahci_platform_ops and ahci_error_handler().

NOTE:
* The hot-plug can't be supported when PDDQ mode is ever enabled.

* module parameter usage how-to:
  - default: enable PDDQ mode when no device detected.
  - add "ahci-imx.hotplug=1" into kernel command line if your don't
    want to enable PDDQ mode when no device detected on the port.

tj: Slightly updated description and comments.

Signed-off-by: Richard Zhu <r65037@freescale.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

drivers/ata/ahci_platform.c

@@ -49,10 +49,11 @@ static struct platform_device_id ahci_devtype[] = {
 };
 MODULE_DEVICE_TABLE(platform, ahci_devtype);
 
-static struct ata_port_operations ahci_platform_ops = {
+struct ata_port_operations ahci_platform_ops = {
 	.inherits	= &ahci_ops,
 	.host_stop	= ahci_host_stop,
 };
+EXPORT_SYMBOL_GPL(ahci_platform_ops);
 
 static struct ata_port_operations ahci_platform_retry_srst_ops = {
 	.inherits	= &ahci_pmp_retry_srst_ops,