staging: mt7621-dts: simplify pcie phy bindings

If each phy port doesn't have its own resources, then we don't need
child nodes. Handle it using #phy-cells to 1 for both phy's.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>