tty: serial: qcom-geni-serial: drop unneeded forward definitions

If we shuffle the code a bit, we can drop all forward definitions of
various static functions.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20221229155030.418800-3-brgl@bgdev.pl


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>