[ARM] 5569/1: at91: Support for at91sam9g45: clocks management

Add the at91sam9g45 series support to the AT91 generic clock file.
This takes care of the particularities of the PMC for this series.
It also takes advantage of the management by functionalities of
those PLLs and clocks.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>