[SLP][NFC]Add avx2 test run, NFC.

Author: alexey-bataev

llvm/test/Transforms/SLPVectorizer/X86/multi-nodes-to-shuffle.ll

@@ -1,5 +1,6 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -passes=slp-vectorizer -S < %s -mtriple=x86_64-unknown-linux -slp-threshold=-107 | FileCheck %s
+; RUN: opt -passes=slp-vectorizer -S < %s -mtriple=x86_64-unknown-linux -slp-threshold=-107 -mattr=+avx2 | FileCheck %s
 
 define void @test(i64 %p0, i64 %p1, i64 %p2, i64 %p3) {
 ; CHECK-LABEL: @test(