[ARM] 3866/1: AT91 clock update

This patch makes the AT91 clock.c support processor-generic (AT91RM9200
and AT91SAM9xxx).  The clocks supported by a particular AT91 processor
are defined in the processor-specific file and are registered with
clock.c at startup.

Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>