drm/dp_mst: Reformat drm_dp_check_act_status() a bit

Just add a bit more line wrapping, get rid of some extraneous
whitespace, remove an unneeded goto label, and move around some variable
declarations. No functional changes here.

Signed-off-by: Lyude Paul <lyude@redhat.com>
[this isn't a fix, but it's needed for the fix that comes after this]
Fixes: ad7f8a1f ("drm/helper: add Displayport multi-stream helper (v0.6)")
Cc: Sean Paul <sean@poorly.run>
Cc: <stable@vger.kernel.org> # v3.17+
Reviewed-by: Sean Paul <sean@poorly.run>
Link: https://patchwork.freedesktop.org/patch/msgid/20200406221253.1307209-3-lyude@redhat.com