clk/qcom: use function pointers for enable and set_rate

Currently, it isn't possible to build clock drivers for more than one
platform due to how the msm_enable() and msm_set_rate() callbacks are
implemented.

Extend qcom_clk_data to include function pointers for these and convert
all platforms to use them.

Previously, clock drivers relied on include/configs/<board.h> to include the
board specific sysmap header, however as most of the header contents are clock
driver related, import the contents directly into each clock driver and
remove the header. The only exception here is the dragonboard820c board file
which includes some pinctrl macros, those are also inlined.

Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
[caleb: remove additional sysmap-sdm845.h mention]