ARM: Kirkwood: Replace clock gating

Add a varient of the basic clk-gate code. This variant calls a
function before gating the clock off. This function is used to disable
the SATA or PCIe PHY.

Now that all the drivers prepare and enable there clk as needed, there
is no need for the common code to keep track of which clocks need
gating on. Let the common clock framework turn off clocks which are
not used.

Buy using the added clk varient, when the clk framework turns off SATA
or PCIe clocks, we also disabled SATA and PCIe PHYs which were not
needed.

The function kirkwood_pcie_id() can now be called outside of __init
code, so remove this property for it, and functions it calls.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Jamie Lentin <jm@lentin.co.uk>
Signed-off-by: Mike Turquette <mturquette@linaro.org>