Use triple's isiOS() and isOSDarwin() methods.

These methods are already used in lots of places. This makes things more
consistent. NFC.

llvm-svn: 219386
diff --git a/llvm/lib/Target/ARM/ARMSubtarget.cpp b/llvm/lib/Target/ARM/ARMSubtarget.cpp
index a26fba1..a3ade98 100644
--- a/llvm/lib/Target/ARM/ARMSubtarget.cpp
+++ b/llvm/lib/Target/ARM/ARMSubtarget.cpp
@@ -395,8 +395,7 @@
 }
 
 bool ARMSubtarget::hasSinCos() const {
-  return getTargetTriple().getOS() == Triple::IOS &&
-    !getTargetTriple().isOSVersionLT(7, 0);
+  return getTargetTriple().isiOS() && !getTargetTriple().isOSVersionLT(7, 0);
 }
 
 // This overrides the PostRAScheduler bit in the SchedModel for any CPU.