[X86] Add User Interrupts(UINTR) instructions

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/D89301
diff --git a/clang/docs/ClangCommandLineReference.rst b/clang/docs/ClangCommandLineReference.rst
index 86bc9f6..6864f60 100644
--- a/clang/docs/ClangCommandLineReference.rst
+++ b/clang/docs/ClangCommandLineReference.rst
@@ -3335,6 +3335,8 @@
 
 .. option:: -mtsxldtrk, -mno-tsxldtrk
 
+.. option:: -muintr, -mno-uintr
+
 .. option:: -mvaes, -mno-vaes
 
 .. option:: -mvpclmulqdq, -mno-vpclmulqdq