Docs: sphinxify device-drivers.tmpl

Perform a basic sphinx conversion of the device-drivers docbook and move it
to its own directory.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/Documentation/index.rst b/Documentation/index.rst
index 05eded5..0d6992b 100644
--- a/Documentation/index.rst
+++ b/Documentation/index.rst
@@ -13,6 +13,7 @@
 
    kernel-documentation
    dev-tools/tools
+   driver-api/drivers
    media/index
    gpu/index