msm: scm: Move the scm driver to drivers/soc/qcom

Architectural changes in the ARM Linux kernel tree mandate
the eventual removal of the mach-* directories. Move the
scm driver to drivers/soc/qcom and the scm header to
include/soc/qcom to support that removal.

Change-Id: Ie660d0566de35045c1ba73fcddeda99efacf057e
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>