drm/msm/dpu: split dpu_encoder_wait_for_event into two functions

Stop multiplexing several events via the dpu_encoder_wait_for_event()
function. Split it into two distinct functions two allow separate
handling of those events.

Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/579848/
Link: https://lore.kernel.org/r/20240226-fd-dpu-debug-timeout-v4-2-51eec83dde23@linaro.org