ieee802154/mrf24j40: Fix alignment of parenthesis

CC: Alan Ott <alan@signal11.us>
Signed-off-by: NStefan Schmidt <s.schmidt@samsung.com>
Acked-by: NAlexander Aring <alex.aring@gmail.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>