The Puma SoM allows to select in hardware directly which storage
medium to try for loading the bootloader, either SPI-NOR followed
by eMMC followed by SD card, or SD card only.

This signal is exposed on the Q7 connector and allows carrierboards
to control it however they want.

This feedback pin allows to know in which state the SoM currently
is and provided the current state isn't modified until next reboot,
know from which storage medium the bootloader could be loaded from
next time.
Signed-off-by: Vahe Grigoryan <vahe.grigoryan@theobroma-systems.com>
Link: https://lore.kernel.org/r/20231214122801.3144180-2-vahe.grigoryan@theobroma-systems.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>