drm/panel: samsung: make vint_table static const

This eliminates the following sparse warning:

drivers/gpu/drm/panel/panel-samsung-s6e3ha2.c:217:15: warning: symbol
'vint_table' was not declared. Should it be static?

While at it, make the table const as it is never modified.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200916132301.2914017-1-yanaijie@huawei.com