boards: arm: nrf5340pdk: fix pin assignments

I2C1 used LED pins rather than the ones in the Arduino header
position.  SPI2 used Arduino D0 for both SCK and MOSI; replace all
pins with D11-D13 which are the standard location for SPI on the
Arduino header.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>