arm64: Add __init section marker to some functions

They are not needed after booting, so mark them as __init to move them
to the .init section.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://lore.kernel.org/r/20210330135449.4dcffd7f@xhacker.debian


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>