[AMDGPU][MC][DOC] Updated AMD GPU assembler description

Stage 2: added detailed description of operands

See bug 36572: https://bugs.llvm.org/show_bug.cgi?id=36572

llvm-svn: 349368
diff --git a/llvm/docs/AMDGPU/gfx9_param.rst b/llvm/docs/AMDGPU/gfx9_param.rst
new file mode 100644
index 0000000..2831a65
--- /dev/null
+++ b/llvm/docs/AMDGPU/gfx9_param.rst
@@ -0,0 +1,22 @@
+..
+    **************************************************
+    *                                                *
+    *   Automatically generated file, do not edit!   *
+    *                                                *
+    **************************************************
+
+.. _amdgpu_synid9_param:
+
+param
+===========================
+
+Interpolation parameter to read:
+
+    ============ ===================================
+    Syntax       Description
+    ============ ===================================
+    p0           Parameter *P0*.
+    p10          Parameter *P10*.
+    p20          Parameter *P20*.
+    ============ ===================================
+