drm/mediatek: mtk_hdmi: Drop redundant clock retrieval in mtk_hdmi_get_cec_dev

drm/mediatek: mtk_hdmi: Drop redundant clock retrieval in mtk_hdmi_get_cec_dev

In mtk_hdmi driver, when the CEC device parsing logic was moved from
mtk_hdmi_dt_parse_pdata function to the new mtk_hdmi_get_cec_dev sub
function, the call to mtk_hdmi_get_all_clk was kept in both functions,
whereas it was only called once in the original mtk_hdmi_dt_parse_pdata
code and does not need to be called a second time.
So, remove this call from mtk_hdmi_get_cec_dev to keep the same sequence
as previously.

Fixes: 7485be967f7f ("drm/mediatek: mtk_hdmi: Move CEC device parsing in new function")
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20251023-mediatek-drm-hdmi-v2-v11-1-7873ec4a1edf@collabora.com/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>