serial: msm-geni: Detect error from get_clk_div_rate

serial: msm-geni: Detect error from get_clk_div_rate

In msm_serial_setbrg if the call to get_clk_div_rate fails then there
will not have been an assignment to clk_div which will lead to the call
to geni_serial_baud using an uninitialised value.
Check for an error from get_clk_div_rate and return an error code if so.

This issue was found by Smatch.

Signed-off-by: Andrew Goodbody <andrew.goodbody@linaro.org>
Reviewed-by: Casey Connolly <casey.connolly@linaro.org>
Link: https://lore.kernel.org/r/20250811-serial_msm_geni-v1-1-4499179491bc@linaro.org
Signed-off-by: Casey Connolly <casey.connolly@linaro.org>