MIPS: lantiq: update the clock alias' for the mainline PCIe PHY driver

The mainline PCIe PHY driver has it's own devicetree node. Update the
clock alias so the mainline driver finds the clocks.

The first PCIe PHY is located at 0x1f106800 and exists on VRX200, ARX300
and GRX390.
The second PCIe PHY is located at 0x1f700400 and exists on ARX300 and
GRX390.
The third PCIe PHY is located at 0x1f106a00 and exists onl on GRX390.
Lantiq's board support package (called "UGW") names these registers
"PDI".

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: john@phrozen.org
Cc: kishon@ti.com
Cc: ralf@linux-mips.org
Cc: robh+dt@kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: hauke@hauke-m.de
Cc: mark.rutland@arm.com
Cc: ms@dev.tdt.de