boards: nrf52_pca10040:  When SPI is required enable SPI_2 by default
boards: nrf52_pca10040:  When SPI is required enable SPI_2 by default

Required by Arduino Uno Rev3 shield connector

Signed-off-by: Nick Ward <e21105bd80467889211288b3ec4c13293a4b5fd6@gmail.com>

zephyrproject-rtos/zephyr,Vudentz/zephyr,finikorg/zephyr,nashif/zephyr,galak/zephyr,nashif/zephyr,galak/zephyr,galak/zephyr,nashif/zephyr,finikorg/zephyr,galak/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,Vudentz/zephyr,galak/zephyr,nashif/zephyr,finikorg/zephyr,Vudentz/zephyr,Vudentz/zephyr,finikorg/zephyr