Fixes sparse warnings:
- warning: symbol 'mtk_vdec_8173_pdata' was not declared. Should it be
static?
- warning: symbol 'mtk_vdec_8183_pdata' was not declared. Should it be
static?

Link: https://lore.kernel.org/linux-media/20210809131940.2890108-1-tzungbi@google.com

Cc: linux-mediatek@lists.infradead.org, linux-media@vger.kernel.org, linux-arm-kernel@lists.infradead.org, tzungbi@google.com # X-LSpam-Score: -10.7 (----------)
Signed-off-by: Tzung-Bi Shih <tzungbi@google.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>