powerpc/QE: use arch_initcall to probe QUICC Engine GPIOs

It was discussed that global arch_initcall() is preferred way to probe
QE GPIOs, so let's use it.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>