[bpf] add big- and host- endian support

Summary:
-march=bpf    -> host endian
-march=bpf_le -> little endian
-match=bpf_be -> big endian

Test Plan:
v1 was tested by IBM s390 guys and appears to be working there.
It bit rots too fast here.

Reviewers: chandlerc, tstellarAMD

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D10177

llvm-svn: 239071
diff --git a/llvm/test/CodeGen/BPF/loops.ll b/llvm/test/CodeGen/BPF/loops.ll
index 4798d78..7a4d5db 100644
--- a/llvm/test/CodeGen/BPF/loops.ll
+++ b/llvm/test/CodeGen/BPF/loops.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -march=bpf | FileCheck %s
+; RUN: llc < %s -march=bpf_le | FileCheck %s
 
 define zeroext i16 @add(i16* nocapture %a, i16 zeroext %n) nounwind readonly {
 entry: