ahci: imx: Add i.MX53 support

Add minor adjustments to support i.MX53 SATA port as well as i.MX6Q one.
The difference here is mostly the clock which need to be enabled and also
the lack of need of programming IOMUXC registers on i.MX53. All of which
is well handles in the clock enable/disable functions. Note that this patch
also cleans up the names of the common functions, so they don't read imx6q_*
but imx_* instead.

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Shawn Guo <shawn.guo@linaro.org>
Cc: Richard Zhu <r65037@freescale.com>
Cc: Linux-IDE <linux-ide@vger.kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>