configs: qualcomm: use fragments for debug UART

configs: qualcomm: use fragments for debug UART

The QCM6490 and QCS9100 targets always enable debug UART, but this is
not really optimal for typical users.

Move these debug UART options to config fragments so that they aren't
enabled by default.

Signed-off-by: Casey Connolly <casey.connolly@linaro.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patch.msgid.link/20250722-b4-qcom-tooling-improvements-v5-6-df143f1247fc@linaro.org
Signed-off-by: Casey Connolly <kcxt@postmarketos.org>