media: mtk-vcodec: fix kernel-doc warnings

media: mtk-vcodec: fix kernel-doc warnings

mtk_vcodec_drv.h:
	It's '@var:', not '@var - '.
	In two places 'struct' was used instead of 'enum'.

vdec_drv_if.h:
	It's '@var:', not '@var :'.
	In one place 'struct' was used instead of 'enum'.

venc_ipi_msg.h:
	It's '@data:', not '@data[8]:', i.e. arrays do not include the
	size in kernel-doc.
	It's '@var:', not 'var:'.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: Alexandre Courbot <acourbot@chromium.org>
Cc: Tiffany Lin <tiffany.lin@mediatek.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>