drm/komeda: Don't flush inactive pipes

HW doesn't allow flushing inactive pipes and raises an MERR interrupt
if you try to do so. Stop triggering the MERR interrupt in the
middle of a commit by calling drm_atomic_helper_commit_planes
with the ACTIVE_ONLY flag.

Reviewed-by: James Qian Wang (Arm Technology China) <james.qian.wang@arm.com>
Signed-off-by: Mihail Atanassov <mihail.atanassov@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191010102950.56253-1-mihail.atanassov@arm.com