drivers/net/ethernet: Fix non-kernel-doc comments with kernel-doc start markers

Convert doxygen (or similar) formatted comments to kernel-doc or
unformatted comment.  Delete a few that are content-free.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>