drm/msm/dp: move interrupt handling to dp_ctrl

It makes it easier to keep all interrupts-related code in dp_ctrl
submodule. Move all functions to dp_ctrl.c.

Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Tested-by: Stephen Boyd <swboyd@chromium.org> # sc7180-trogdor
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/654330/
Link: https://lore.kernel.org/r/20250518-fd-dp-audio-fixup-v6-10-2f0ec3ec000d@oss.qualcomm.com