arm: pxa: Transition pxa27x to clk framework

Transition the PXA27x CPUs to the clock framework.
This transition still enables legacy platforms to run without device
tree as before, ie relying on platform data encoded in board specific
files.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Mike Turquette <mturquette@linaro.org>