ARM: 5769/1: CPU_ARM920T: remove dead Maverick EP9312 URL

Remove the URL listed for Maverick EP9312 since it is not available
and modify the help text appropriately.

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>