Clang: adjust MMX instrinsics release note.

Author: jyknight

clang/docs/ReleaseNotes.rst

@@ -178,7 +178,9 @@ X86 Support
   unconditionally. These intrinsics are therefore *no longer
   supported* if MMX is enabled without SSE2 -- either from targeting
   CPUs from the Pentium-MMX through the Pentium 3, or explicitly via
-  passing arguments such as ``-mmmx -mno-sse2``.
+  passing arguments such as ``-mmmx -mno-sse2``. MMX assembly code
+  remains supported without requiring SSE2, including inside
+  inline-assembly.
 
 - The compiler builtins such as ``__builtin_ia32_paddb`` which
   formerly implemented the above MMX intrinsic functions have been