media: platform: mtk-mdp3: extend shared memory structure to 4-byte aligned

The communication between MDP3 kernel driver and SCP is pass through
a shared memory, and the data structure is defined in the "mtk-img-ipi.h".
However, there is a 4-byte read limit in further SCP hardware, so the
data structure should be in 4-byte aligned.

Signed-off-by: Moudy Ho <moudy.ho@mediatek.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>