X86: silence warning (-Wparentheses)

GCC 4.8.2 points out the ambiguity in evaluation of the assertion condition:

lib/Target/X86/X86FloatingPoint.cpp:949:49: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses]
   assert(STReturns == 0 || isMask_32(STReturns) && N <= 2);

llvm-svn: 214672
diff --git a/llvm/lib/Target/X86/X86FloatingPoint.cpp b/llvm/lib/Target/X86/X86FloatingPoint.cpp
index e74613b..aac7ec7 100644
--- a/llvm/lib/Target/X86/X86FloatingPoint.cpp
+++ b/llvm/lib/Target/X86/X86FloatingPoint.cpp
@@ -946,7 +946,7 @@
 
   // FP registers used for function return must be consecutive starting at
   // FP0.
-  assert(STReturns == 0 || isMask_32(STReturns) && N <= 2);
+  assert((STReturns == 0 || isMask_32(STReturns)) && N <= 2);
 
   for (unsigned I = 0; I < N; ++I)
     pushReg(N - I - 1);