ARM: fix VFP asm constraints

Summary:
Rich Felker was sad that clang used 'w' and 'P' for VFP constraints when GCC documents them as 't' and 'w':
  https://gcc.gnu.org/onlinedocs/gcc/Machine-Constraints.html

This was added way back in 2008:
  http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20080421/005393.html

Subscribers: aemerson, rengolin, cfe-commits

Differential Revision: http://reviews.llvm.org/D17349

llvm-svn: 261309

clang/lib/Basic/Targets.cpp

@@ -4939,8 +4939,8 @@ public:
     default: break;
     case 'l': // r0-r7
     case 'h': // r8-r15
-    case 'w': // VFP Floating point register single precision
-    case 'P': // VFP Floating point register double precision
+    case 't': // VFP Floating point register single precision
+    case 'w': // VFP Floating point register double precision
       Info.setAllowsRegister();
       return true;
     case 'I':