AMDGPU: Remove optnone from a test

It's not clear why the test had this. I'm unable to break the original
case with the original patch reverted with or without optnone.

This avoids a failure in a future commit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@375321 91177308-0d34-0410-b5e6-96231b3b80d8

test/CodeGen/AMDGPU/extract-subvector-equal-length.ll

@@ -4,7 +4,7 @@
 ; Test for ICE in SelectionDAG::computeKnownBits when visiting EXTRACT_SUBVECTOR
 ; with DemandedElts already as wide as the source vector.
 
-define <3 x i32> @quux() #0 {
+define <3 x i32> @quux() {
 ; CHECK-LABEL: quux:
 ; CHECK:       ; %bb.0: ; %bb
 ; CHECK-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
@@ -26,5 +26,3 @@ bb:
   %tmp10 = lshr <3 x i32> %tmp9, <i32 1, i32 1, i32 1>
   ret <3 x i32> %tmp10
 }
-
-attributes #0 = { noinline optnone }