ARM: davinci: cp-intc: request the memory region before remapping it

Add a missing call to request_mem_region() before calling ioremap() to
make sure it's not been requested by another user.

Reviewed-by: David Lechner <david@lechnology.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>