[NET]: make function pointer argument parseable by kernel-doc

When a function takes a function pointer as argument it should use the 'return
(*pointer)(params...)' syntax used everywhere else in the kernel as this is
recognized by kernel-doc.

Signed-off-by: Martin Waitz <tali@admingilde.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>