staging: fsl-dpaa2/ethsw: do not force user to bring interface down

staging: fsl-dpaa2/ethsw: do not force user to bring interface down

Link settings can be changed only when the interface is down. Disable
and re-enable the interface, if necessary, behind the scenes so that we do
not force users to an if down/up sequence.

Reported-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Link: https://lore.kernel.org/r/1565700187-16048-11-git-send-email-ioana.ciornei@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>