arm64: dts: imx8m{m, n}-venice-gw7902: add gpio pins for new board revision

Add gpio pins present on new board revision:
 * LTE modem support (imx8mm-gw7902 only)
  - lte_pwr#
  - lte_rst
  - lte_int
 * M2 power enable
  - m2_pwr_en
 * off-board 4.0V supply
  - vdd_4p0_en

Signed-off-by: Tim Harvey <tharvey@gateworks.com>