media: platform: mtk-mdp3: fix uninitialized variable in mdp_path_config()

Fix the build warnings that were detected by the linux-media
build scripts tool:

drivers/media/platform/mediatek/mdp3/mtk-mdp3-cmdq.c:
	In function 'mdp_path_config.isra':
drivers/media/platform/mediatek/mdp3/mtk-mdp3-cmdq.c:
	warning: 'ctx' may be used uninitialized [-Wmaybe-uninitialized]
      |                    out = CFG_COMP(MT8195, ctx->param, outputs[0]);
      |                                           ~~~^~~~~~~
drivers/media/platform/mediatek/mdp3/mtk-img-ipi.h: note:
	in definition of macro 'CFG_COMP'
      |         (IS_ERR_OR_NULL(comp) ? 0 : _CFG_COMP(plat, comp, mem))
      |                         ^~~~
drivers/media/platform/mediatek/mdp3/mtk-mdp3-cmdq.c:
	note: 'ctx' was declared here
      |         struct mdp_comp_ctx *ctx;
      |

Fixes: 61890cca ("media: platform: mtk-mdp3: add MediaTek MDP3 driver")
Signed-off-by: Moudy Ho <moudy.ho@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>