drm/bridge: synopsys: dw-hdmi: also allow interlace on bridge

Since we allow interlace on the encoder, also allow it on the bridge
so we can allow interlaced modes when using DRM_BRIDGE_ATTACH_NO_CONNECTOR.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20211014152606.2289528-5-narmstrong@baylibre.com