powerpc/bpf: Remove classical BPF support for PPC32

At the time being, PPC32 has Classical BPF support.

The test_bpf module exhibits some failure:

	test_bpf: #298 LD_IND byte frag jited:1 ret 202 != 66 FAIL (1 times)
	test_bpf: #299 LD_IND halfword frag jited:1 ret 51958 != 17220 FAIL (1 times)
	test_bpf: #301 LD_IND halfword mixed head/frag jited:1 ret 51958 != 1305 FAIL (1 times)
	test_bpf: #303 LD_ABS byte frag jited:1 ret 202 != 66 FAIL (1 times)
	test_bpf: #304 LD_ABS halfword frag jited:1 ret 51958 != 17220 FAIL (1 times)
	test_bpf: #306 LD_ABS halfword mixed head/frag jited:1 ret 51958 != 1305 FAIL (1 times)

	test_bpf: Summary: 371 PASSED, 7 FAILED, [119/366 JIT'ed]

Fixing this is not worth the effort. Instead, remove support for
classical BPF and prepare for adding Extended BPF support instead.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/fbc3e4fcc9c8f6131d6c705212530b2aa50149ee.1616430991.git.christophe.leroy@csgroup.eu