ARM: at91: soc: Add init_time callback

Introduce an init_time callback to the at91_init_soc structure to be able to
tweak the init_time machine callback on a per-soc basis, instead of having to
rely on a global one.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

Conflicts:
	arch/arm/mach-at91/setup.c