ARM: 6278/2: fix regression in RealView after the introduction of pclk

The patch to add the apb_pclk to the AMBA/PrimeCell bus broke
RealView, since the clockdevice is not registered at probe() time.
This moves clock initialization to a core_initcall()

[rmk:moved before the problematical commit to avoid bisect problems]

Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>