clk/qcom: move from mach-snapdragon

clk/qcom: move from mach-snapdragon

Clock drivers don't belong here, move them to the right place and
declutter mach-snapdragon a bit.

To de-couple these drivers from specific "target" platforms, add
additional config options to enable each clock driver gated behind a
common CLK_QCOM option and enable them by default for the respective
targets. This will make future work easier as we move towards a generic
Qualcomm target.

Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>