msm: clock-a7: Change init call to subsys_initcall

clock-a7 plays a critical role in scaling cpu frequency. It needs
to be ready early. It's empirical to probe it right after its dependency
is met (clock driver). Therefore, move it to subsys_initcall level.

Change-Id: Ia6b2b55642ca6682e4c31bfaf6493d5f61430405
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>