drm/exynos: fix incorrect interrupt induced by m2m operation.

This patch fixes incorrect interrupt induced by m2m operation.
the m2m operation calls s/w reset every frame but there is the case that
the interrupt to m2m operation occures after s/w reset sometimes.
So this patch makes dma and capture operations stop at s/w reset
to avoid incorrect interrupt.

Signed-off-by: Jinyoung Jeon <jy0.jeon@samsung.com>
Signed-off-by: Eunchul Kim <chulspro.kim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>