[X86] Add HRESET instruction.

For more details about these instructions, please refer to the latest ISE document: https://software.intel.com/en-us/download/intel-architecture-instruction-set-extensions-programming-reference.

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D89102
diff --git a/clang/docs/ClangCommandLineReference.rst b/clang/docs/ClangCommandLineReference.rst
index 10e0203..ff3decb 100644
--- a/clang/docs/ClangCommandLineReference.rst
+++ b/clang/docs/ClangCommandLineReference.rst
@@ -3261,6 +3261,8 @@
 
 .. option:: -mgfni, -mno-gfni
 
+.. option:: -mhreset, -mno-hreset
+
 .. option:: -minvpcid, -mno-invpcid
 
 .. option:: -mkl, -mno-kl