drm: bridge: it66121: Remove redundant check

ctx->next_bridge is checked for NULL twice in a row. The second
conditional is redundant, so remove it.

Signed-off-by: Drew Davenport <ddavenport@chromium.org>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220114064012.1670612-1-ddavenport@chromium.org