staging: mt7621-dts: add pcie controller port registers

The pcie node of the device tree only contains registers
for the host-bridge and pcie port 0. Add the pcie port 1
and pcie port 2 also.

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