clk: qcom: gcc: Update the TCXO source map value sm8150

The enable_safe_config flag if used in the RCG assumes the TCXO source map
to be '0', which otherwise would cause mapping it to incorrect source
during clk_disable.

Change-Id: I7007314f5772a028ab9d1acf755c35a3998dbc2e
Signed-off-by: Taniya Das <tdas@codeaurora.org>