ozone: drm: Clear pending planes on bounds changes
ozone: drm: Clear pending planes on bounds changes

When the dimensions of the DriWindow changes the intention was to free
any pending planes. Unfortunately the condition to check for this would
never be true due to the assignment happening before the check

TEST=Boot amd64-generic image and hotplug/unplug screen.
BUG=none

Review URL: https://codereview.chromium.org/1404853004

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#354260}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk