drm/msm/dp: Simplify aux irq handling code

drm/msm/dp: Simplify aux irq handling code

We don't need to stash away 'isr' in the aux structure to pass to two
functions. Let's use a local variable instead. And we can complete the
completion variable in one place instead of two to simplify the code.

Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: Abhinav Kumar <abhinavk@codeaurora.org>
Cc: Kuogee Hsieh <khsieh@codeaurora.org>
Cc: aravindh@codeaurora.org
Cc: Sean Paul <sean@poorly.run>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Kuogee Hsieh <khsieh@codeaurora.org>
Link: https://lore.kernel.org/r/20210507212505.1224111-2-swboyd@chromium.org
Signed-off-by: Rob Clark <robdclark@chromium.org>