bpf: fix bug on silently truncating 64-bit immediate

We came across an llvm bug when compiling some testcases that 64-bit
immediates are silently truncated into 32-bit and then packed into
BPF_JMP | BPF_K encoding.  This caused comparison with wrong value.

This bug looks to be introduced by r308080 (llvm 5.0). The Select_Ri pattern is
supposed to be lowered into J*_Ri while the latter only support 32-bit
immediate encoding, therefore Select_Ri should have similar immediate
predicate check as what J*_Ri are doing.

The bug is fixed by
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@315889

 91177308-0d34-0410-b5e6-96231b3b80d8
in llvm 6.0.

This patch is largely the same as the fix in llvm 6.0 except
one minor adjustment for the test case.

Reported-by: John Fastabend <john.fastabend@gmail.com>
Reported-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Reviewed-by: Yonghong Song <yhs@fb.com>
llvm-svn: 319633