arm: dove: Use correct GPIO_BASE and remove orion_gpio_init() leftover

commit 9eac6d0a

 (ARM: Remove dependency of plat-orion GPIO code on mach
directory includes) missed to convert one instance of
DOVE_GPIO_VIRT_BASE and left the orion_gpio_init() in mpp.c

Fix it up.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>