Add clock binding information for primecell peripherals. For most, a
clock input name of "apb_pclk" is required. Any primecell peripherals
which are different will need to be documented separately.
Signed-off-by: NRob Herring <rob.herring@calxeda.com>
Signed-off-by: NMike Turquette <mturquette@linaro.org>