drm/mediatek: using new factor for tvdpll for MT2701 hdmi phy

This is the second step to make MT2701 HDMI stable.
The factor depends on the divider of DPI in MT2701, therefore,
we should fix this factor to the right and new one.
Test: search ok

Signed-off-by: Wangyan Wang <wangyan.wang@mediatek.com>
Signed-off-by: CK Hu <ck.hu@mediatek.com>