clk/qcom: sdm845: add register map for simple gate clocks

Many gate clocks can be enabled with a single register write, add support
for defining these simple gate clocks and add the ones found on SDM845.

While we're here, inline clk_init_uart() into msm_set_rate().

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