[ARM] 3959/1: AT91: Support for SAM9 USB and HCK clocks

The bits used to select the USB clocks are different on the SAM9's.
Add support for the HCK clocks on the AT91SAM9261.

Patch from Patrice Vilchez & Nicolas Ferre

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