disco_l475_iot1: Enable bt chip

Enable BlueNRJ chip on disco_l475_iot1 board.
Communication with SoC, is done over SPI(3). Hence this
commit enables SPI3 on SoC and configure BT_SPI IRQ,
RESET and CS pins.

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>
2 files changed