sparc: bpf_jit: add support for BPF_LD(X) | BPF_LEN instructions

BPF_LD | BPF_W | BPF_LEN instruction is occasionally used by tcpdump
and present in 11 tests in lib/test_bpf.c
Teach sparc JIT compiler to emit it.

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>