ARM: net: make BPF_LD | BPF_IND instruction trigger r_X initialisation to 0.

Without this patch, if the only instructions using r_X are of the
BPF_LD | BPF_IND type, r_X would not be reset to 0, using whatever
value was there when entering the jited code. With this patch, r_X
will be correctly marked as used so it will be reset to 0 in the
prologue code.

This fix also makes the test "LD_IND byte default X" pass in the
test_bpf module when the ARM JIT is enabled.

Signed-off-by: Nicolas Schichan <nschichan@freebox.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>