bpf, ppc64: remove obsolete exception handling from div/mod

Since we've changed div/mod exception handling for src_reg in
eBPF verifier itself, remove the leftovers from ppc64 JIT.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>