netdev: bfin_mac: add support for IEEE 1588 PTP

Newer on-chip MAC peripherals support IEEE 1588 PTP in the hardware, so
extend the driver to support this functionality.

Signed-off-by: Barry Song <barry.song@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: David S. Miller <davem@davemloft.net>