[ARM] 5609/1: ep93xx: add register defines for keypad support

Add missing register defines for ep93xx keypad clock support.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Ryan Mallon <ryan@bluewatersys.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>