ARM: bcm2835: Skip doing our own iotable_init() initialization

The only thing we were using this 16MB mapping of IO peripherals for
was the uart's early debug mapping.  If we just drop the map_io hook,
the kernel will call debug_ll_io_init() for us, which maps the single
page needed for the device.

Signed-off-by: Eric Anholt <eric@anholt.net>
Tested-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>