[docs] Update doc after split of -gen-intrinsic in r335407

llvm-svn: 335515
diff --git a/llvm/docs/CommandGuide/tblgen.rst b/llvm/docs/CommandGuide/tblgen.rst
index a42b04d..c23af5e 100644
--- a/llvm/docs/CommandGuide/tblgen.rst
+++ b/llvm/docs/CommandGuide/tblgen.rst
@@ -109,9 +109,13 @@
 
  Generate subtarget enumerations.
 
-.. option:: -gen-intrinsic
+.. option:: -gen-intrinsic-enums
 
- Generate intrinsic information.
+ Generate intrinsic enums.
+
+.. option:: -gen-intrinsic-impl
+
+ Generate intrinsic implementation.
 
 .. option:: -gen-tgt-intrinsic