dts: nordic: Fix ngpios for nRF54L15 (and variants) The correct number is 7, since the QFN52 (QGAA) variant has P0.00 to P0.06 present. See: https://docs.nordicsemi.com/bundle/ps_nrf54L15/page/chapters/pin.html#ariaid-title6 Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>