Fix incorrect Cygnus UART2 register base.

Fixes: 0f0b21a8 ("ARM: dts: Move all Cygnus peripherals into axi bus")
Signed-off-by: Ray Jui <ray.jui@broadcom.com>
Signed-off-by: Scott Branden <scott.branden@broadcom.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>