docs: mention that coding style can differ between drivers

... and point people to use/honour the EditorConfig/Emacs files, where
applicable.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

docs/devinfo.html

@@ -30,6 +30,12 @@
 <p>
 Mesa is over 20 years old and the coding style has evolved over time.
 Some old parts use a style that's a bit out of date.
+
+Different sections of mesa can use different coding style as set in the local
+EditorConfig (.editorconfig) and/or Emacs (.dir-locals.el) file.
+
+Alternatively the following is applicable.
+
 If the guidelines below don't cover something, try following the format of
 existing, neighboring code.
 </p>