clk: qcom: Check for errors during RCG read

There could be instances where the RCG configuration update or readback
could fail. Notify the caller of the failure. Add support to change
scope of mux_div_get_src_div() in order to use it globally.

Change-Id: Ica07c28cede695785db81697effcb40ab6b717d4
Signed-off-by: Amit Nischal <anischal@codeaurora.org>