SPIBus.h

Squashed commit of the following:

commit 2a57b6ab
Author: Luca Erbetta <luca.erbetta105@gmail.com>
Date:   Mon Apr 26 23:43:56 2021 +0200

    Fixed mxgui path in gitmodules

commit d5f245a6
Merge: 58cfbe74 dd1c7543
Author: Luca Erbetta <luca.erbetta@skywarder.eu>
Date:   Mon Apr 26 21:39:15 2021 +0000

    Merge branch 'xbee-rework' into 'testing'

    [Xbee] Driver Rework & GUI to perform antenna test

    See merge request scs/skyward-boardcore!59

commit dd1c7543
Author: Luca Erbetta <luca.erbetta@skywarder.eu>
Date:   Mon Apr 26 21:39:14 2021 +0000

    [Xbee] Driver Rework & GUI to perform antenna test

commit 58cfbe74
Author: luca.conterio <luca.conterio@skywarder.eu>
Date:   Sat Apr 24 20:13:33 2021 +0200

    [SDCard] SDCard Benchmark