media: mediatek: vcodec/venc: return 0 instead of 'ret'.

Since 'ret' is known to be 0, just return '0'. This fixes a smatch warning:

venc_h264_if.c:568 h264_encode_frame() warn: missing error code? 'ret'

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: Andrew-CT Chen <andrew-ct.chen@mediatek.com>
Cc: Yunfei Dong <yunfei.dong@mediatek.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>