mac802154: remove driver ops in wpan-phy

This patch removes the driver ops callbacks inside of wpan_phy struct.
It was used to check if a phy supports this driver ops call. We do this
now via hardware flags.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>