ARM: davinci: aintc: request memory region before remapping it

Add a missing call to request_mem_region() before calling ioremap() to
make sure the region is not being used by anyone else.

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