bpf jit: Make the filter.c::__load_pointer helper non-static for the jits

The function is renamed to make it a little more clear what it does.
It is not added to any .h because it is not for general consumption, only for
bpf internal use (and so by the jits).

Signed-of-by: Jan Seiffert <kaffeemonster@googlemail.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>

Signed-off-by: David S. Miller <davem@davemloft.net>