phy: phy-mtk-tphy: Update names and format of kernel-doc comments

phy: phy-mtk-tphy: Update names and format of kernel-doc comments

mtk_phy_pdata documentation does not use correct tag for struct, while at
it fix one of member wrongly documented.

Warning: drivers/phy/mediatek/phy-mtk-tphy.c:289 cannot understand function prototype: 'struct mtk_phy_pdata'
Warning: drivers/phy/mediatek/phy-mtk-tphy.c:296 struct member 'slew_ref_clock_mhz' not described in 'mtk_phy_pdata'

Link: https://patch.msgid.link/20260223071032.408425-1-vkoul@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>