clk: qcom: rcg2: Remove support for update_src_map

The commit 7533b7fb ("clk: qcom: clk-rcg2: Read RCG source before
calculating clk rate")' had introduced a function to update the src map,
but there could be a race where a set_rate for a clock from a particular
CC on a CPU could override the global cxo_f which was set by clock
enable/disable for a clock from another CC.

Change-Id: Id86818895e226a387e7fd1a09e2034eee18fd361
Signed-off-by: Taniya Das <tdas@codeaurora.org>