net: ethernet: xilinx: Drop kernel doc comment about return value

During review of the patch that became 2e0ec0af ("net: ethernet:
xilinx: Convert to platform remove callback returning void") in
net-next, Radhey Shyam Pandey pointed out that the change makes the
documentation about the return value obsolete. The patch was applied
without addressing this feedback, so here comes a fix in a separate
patch.

Fixes: 2e0ec0af ("net: ethernet: xilinx: Convert to platform remove callback returning void")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>