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