[FPEnv][PowerPC] Correct strictfp test.

Correct llvm-reduce strictfp test to follow the rules documented in the
LangRef:
https://llvm.org/docs/LangRef.html#constrained-floating-point-intrinsics

This test needed the strictfp attribute added to function definitions.

Test changes verified with D146845.

Author: kpneal

llvm/test/CodeGen/PowerPC/ctrloop-constrained-fp.ll

@@ -2,7 +2,7 @@
 ; RUN: llc -mtriple powerpc64le < %s | FileCheck %s
 
 ; Check constrained ops converted to call
-define void @test(ptr %cast) {
+define void @test(ptr %cast) strictfp {
 ; CHECK-LABEL: test:
 ; CHECK:       # %bb.0: # %root
 ; CHECK-NEXT:    mflr 0
@@ -51,7 +51,7 @@ for.body:
 }
 
 ; Check constrained ops converted to native instruction
-define void @test2(ptr %cast) {
+define void @test2(ptr %cast) strictfp {
 ; CHECK-LABEL: test2:
 ; CHECK:       # %bb.0: # %entry
 ; CHECK-NEXT:    li 4, 255