drm/mediatek: Test component initialization earlier in the function mtk_drm_crtc_create

The initialization is currently tested in a later stage in
the function for no reason.
In addition, the test '!comp' will never fail since comp is
set with the '&' operator. Instead, test if a comp was not
initialized by testing "!comp->dev".

Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>