This patch supports BPF_NEG under both BPF_ALU64 and BPF_ALU. LLVM recently
starts to generate it.

NOTE: BPF_NEG takes single operand which is an register and serve as both
input and output.
Signed-off-by: NJiong Wang <jiong.wang@netronome.com>
Reviewed-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>