clock-a7: Move clock-a7 to drivers/clk/qcom

Architecutural changes in the ARM Linux kernel tree mandate the
eventual removal of the mach-* directories. Move mach/clock-a7.c
to drivers/clk/qcom.

Change-Id: I8754f61d0c0ad563287049ac2c6f63aeb6240120
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>