dt-bindings: phy: mediatek,tphy: add support type of SGMII

Add support ethernet SGMII, forgot to update type supported.

Fixes: c01608b3 ("dt-bindings: phy: mediatek: tphy: support type switch by pericfg")
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/20220914060746.10004-1-chunfeng.yun@mediatek.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>