powerpc/bpf ppc32: Do not emit zero extend instruction for 64-bit BPF_END

Suppress emitting zero extend instruction for 64-bit BPF_END_FROM_[L|B]E
operation.

Fixes: 51c66ad ("powerpc/bpf: Implement extended BPF on PPC32")
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b4e3c3546121315a8e2059b19a1bda84971816e4.1633464148.git.naveen.n.rao@linux.vnet.ibm.com

Author: rnav

arch/powerpc/net/bpf_jit_comp32.c

@@ -1107,7 +1107,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
 			return -EOPNOTSUPP;
 		}
 		if (BPF_CLASS(code) == BPF_ALU && !fp->aux->verifier_zext &&
-		    !insn_is_zext(&insn[i + 1]))
+		    !insn_is_zext(&insn[i + 1]) && !(BPF_OP(code) == BPF_END && imm == 64))
 			EMIT(PPC_RAW_LI(dst_reg_h, 0));
 	}