doc: convert UIO howto from docbook to sphinx

Converted with tmplcvt. Only some tiny things needed manual fixing.

Signed-off-by: Alexander Dahl <post@lespocky.de>
Cc: Hans-Jürgen Koch <hjk@hansjkoch.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index be8de24..6f6efd2 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12966,7 +12966,7 @@
 M:	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
-F:	Documentation/DocBook/uio-howto.tmpl
+F:	Documentation/driver-api/uio-howto.rst
 F:	drivers/uio/
 F:	include/linux/uio*.h