test: bpf: expand DIV_KX to DIV_MOD_KX

Expand DIV_KX to use BPF_MOD operation in the
DIV_KX bpf 'classic' test.

CC: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: Denis Kirjanov <kda@linux-powerpc.org>
Signed-off-by: David S. Miller <davem@davemloft.net>