net: mac802154: Set durations automatically

As depicted in the IEEE 802.15.4 specification, modulation/bands are
tight to a number of page/channels so we can for most of them derive the
durations automatically.

The two locations that must call this new helper to set the variou
symbol durations are:
- when manually requesting a channel change though the netlink interface
- at PHY creation, once the device driver has set the default
  page/channel

If an information is missing, the symbol duration is not touched, a
debug message is eventually printed. This keeps the compatibility with
the unconverted drivers for which it was too complicated for me to find
their precise information. If they initially provided a symbol duration,
it would be kept. If they don't, the symbol duration value is left
untouched.

Once the symbol duration derived, the lifs and sifs durations are
updated as well.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20220201180629.93410-4-miquel.raynal@bootlin.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>