ARM: at91/dt: define sam9x5 clocks

Define sam9x5 clocks in sam9x5 dt files and make use of them in peripheral
definitions.

Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>