bpf: doc: "neg" opcode has no operands

Fixes a copy-paste-o in the BPF opcode table: "neg" takes no arguments
and thus has no addressing modes.

Signed-off-by: Dave Anderson <[e-mail]>
Signed-off-by: Kees Cook <[e-mail]>
Acked-by: Alexei Starovoitov <[e-mail]>
Acked-by: Daniel Borkmann <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/networking/filter.txt

···
   mul              0, 4                 A * <x>
   div              0, 4                 A / <x>
   mod              0, 4                 A % <x>
-  neg              0, 4                 !A
+  neg                                   !A
   and              0, 4                 A & <x>
   or               0, 4                 A | <x>
   xor              0, 4                 A ^ <x>