drm/exynos: Fix G2D core malfunctioning issue

drm/exynos: Fix G2D core malfunctioning issue

This patch fixes G2D core malfunctioning issue once g2d dma is started.
Without 'DMA_HOLD_CMD_REG' register setting, there is only one interrupt
after the execution to all command lists have been completed. And that
induces watchdog. So this patch sets 'LIST_HOLD' command to the register
so that command execution interrupt can be occured whenever each command
list execution is finished.

Changelog v2:
- Consider for interrupt setup to each command list and all command lists
  And correct typo.

Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>