drm/mediatek: mtk_hdmi: Remove goto in mtk_hdmi_clk_enable_audio()

If the clk_prepare_enable() call for the SPDIF clock fails, just
disable and unprepare the clock in the error check branch and
return immediately instead of jumping to the end with a goto,
slightly reducing code size.

This commit brings no functional changes.

Reviewed-by: CK Hu <ck.hu@mediatek.com>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/20250217154836.108895-32-angelogioacchino.delregno@collabora.com/


Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>