boards: nordic: Arduino SPI high drive strength

All nRF development kits have long traces from the SoC to the Arduino
header. Set the drive strength on the SPI ports to high to increase the
chances that the default SPI frequency defined in shields works without
errors.

This aligns the remaining DKs with the nRF91 DKs.

Signed-off-by: Jordan Yates <jordan@embeint.com>
5 files changed