docs/reference: clarify wording of BootSlot property contents
docs/reference: clarify wording of BootSlot property contents

Signed-off-by: Christopher Obbard <0becaf7888cff31ba54e40b1ffb8263e09b8b7da@collabora.com>
Signed-off-by: Enrico Jorns <a2e5f936c390f36494e46e71bcfbe365bb1e8c49@pengutronix.de>

ejoerns/rauc,rauc/rauc,rauc/rauc,rauc/rauc,jluebbe/rauc,ejoerns/rauc,jluebbe/rauc,ejoerns/rauc,jluebbe/rauc