mac802154: cleanup ieee802154 hardware flags

This patch changes the ieee802154 hardware flags to enums and setting the
flag values with the BIT macro. Additional this patch changes the
commenting style for matching usual kernel style.

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