Add a README.md file

ao2 · ao2 · commit 739cfca5e937 · 2015-10-02T23:29:59.000+02:00
Some users do not know about the mainline merge and keep proposing updates to
this old repository.

Make thing clearer in the README file
diff --git a/README.md b/README.md
@@ -0,0 +1,6 @@
+This driver is available in mainline linux since v3.11 under sound/usb/hiface/
+
+Make sure to enable SND_USB_HIFACE to have it built.
+
+This out-of-tree driver is just to keep an history of the development and
+for poeple using kernels older than 3.11
