ARM: keystone2: move platform notifier initialisation into platform init

We ideally want the init_meminfo function to do nothing but return the
delta to be applied to PHYS_OFFSET - it should do nothing else.  As we
can detect in platform init code whether we are running in the high
physical address space, move the platform notifier initialisation
entirely into the platform init code.

Acked-by: Santosh Shilimkar <ssantosh@kernel.org>
Tested-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>