documentation: move mtrr.txt to Doc/x86/ subdir

Move mtrr.txt to the Documentation/x86/ subdirectory.
Add 00-INDEX to the Documentation/x86/ subdirectory.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/Documentation/x86/00-INDEX b/Documentation/x86/00-INDEX
new file mode 100644
index 0000000..dbe3377
--- /dev/null
+++ b/Documentation/x86/00-INDEX
@@ -0,0 +1,4 @@
+00-INDEX
+	- this file
+mtrr.txt
+	- how to use x86 Memory Type Range Registers to increase performance