Documentation for atmel-pmc only list one compatible, add the remaining
compatible strings.
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

Specified the main Oscillator via clock binding.
This will allow to do not hardcode it anymore in the DT board at 12MHz.
Signed-off-by: NJean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: NRob Herring <rob.herring@calxeda.com>
Acked-by: NNicolas Ferre <nicolas.ferre@atmel.com>