mrf24j40: add promiscuous mode support

This patch adds support for promiscuous mode by setting promiscuous (no
frame filtering), disable automatic ack handling and not filtering
frames where the crc is invalid.

Reviewed-by: Stefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>