MAINTAINERS: update MediaTek PHY/USB entry

Due to the phy/usb bindings are converted into YAML schema and
also renamed, update entries.
Meanwhile add drivers/usb/host/mtk-xhci* files.
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/20201225075258.33352-11-chunfeng.yun@mediatek.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

MAINTAINERS

@@ -2091,7 +2091,7 @@ M:	Chunfeng Yun <chunfeng.yun@mediatek.com>
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
 L:	linux-mediatek@lists.infradead.org (moderated for non-subscribers)
 S:	Maintained
-F:	Documentation/devicetree/bindings/phy/phy-mtk-*
+F:	Documentation/devicetree/bindings/phy/mediatek,*
 F:	drivers/phy/mediatek/
 
 ARM/Microchip (AT91) SoC support
@@ -11269,6 +11269,8 @@ L:	linux-usb@vger.kernel.org
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
 L:	linux-mediatek@lists.infradead.org (moderated for non-subscribers)
 S:	Maintained
+F:	Documentation/devicetree/bindings/usb/mediatek,*
+F:	drivers/usb/host/xhci-mtk*
 F:	drivers/usb/mtu3/
 
 MEGACHIPS STDPXXXX-GE-B850V3-FW LVDS/DP++ BRIDGES