lantiq: Convert Zyxel P-2812HNU-FX and TP-Link TD-W8970 to support dwc2

lantiq: Convert Zyxel P-2812HNU-FX and TP-Link TD-W8970 to support dwc2

Here the device tree entry for ifxhcd is listed as compatible with one
supported in dwc2 (after patching the dwc driver appropriately).

A second entry is added to support the second core of the hcd. This
entry is listed to be compatible with only dwc2. Done this way there
should be backwards support for both hcd drivers (ltq-hcd and dwc2)

Signed-off-by: Antti Seppälä <a.seppala@gmail.com>
Signed-off-by: Vincent Pelletier <plr.vincent@gmail.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@44676 3c298f89-4303-0410-b956-a3cf2f4a3e73