drm/meson: add support for 1080p25 mode

This essential mode for PAL users is missing, so add it.

Fixes: 335e3713 ("drm/meson: Add support for HDMI venc modes and settings")
Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1542793169-13008-1-git-send-email-christianshewitt@gmail.com


Signed-off-by: Sean Paul <seanpaul@chromium.org>