[test] Don't generate extra file for regalloc-amdgpu.mir test.

Author: hokein

llvm/test/tools/llc/new-pm/regalloc-amdgpu.mir

@@ -1,5 +1,5 @@
 # REQUIRES: amdgpu-registered-target
-# RUN: llc -mtriple=amdgcn --passes='regallocfast<filter=sgpr>' --print-pipeline-passes %s | FileCheck %s --check-prefix=PASS
+# RUN: llc -mtriple=amdgcn --passes='regallocfast<filter=sgpr>' --print-pipeline-passes --filetype=null %s | FileCheck %s --check-prefix=PASS
 # RUN: not llc -mtriple=amdgcn --passes='regallocfast<filter=bad-filter>' --print-pipeline-passes --filetype=null %s 2>&1 | FileCheck %s --check-prefix=BAD-FILTER
 
 # PASS: regallocfast<filter=sgpr>