x86: bpf_jit: fix FROM_BE16 and FROM_LE16/32 instructions

FROM_BE16:
'ror %reg, 8' doesn't clear upper bits of the register,
so use additional 'movzwl' insn to zero extend 16 bits into 64

FROM_LE16:
should zero extend lower 16 bits into 64 bit

FROM_LE32:
should zero extend lower 32 bits into 64 bit

Fixes: 89aa0758

 ("net: sock: allow eBPF programs to be attached to sockets")
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>