Available timeslots masks define timeslots available for the related
channel. These timeslots are defined by the QMC binding.

Timeslots used are initialized to available timeslots but can be a
subset of available timeslots.
This prepares the dynamic timeslots management (ie. changing timeslots
at runtime).
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://lore.kernel.org/r/20231205152116.122512-8-herve.codina@bootlin.com