doc: random number generation

Add random number generation APIs to the HTML documentation.
Fix style issues.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/MAINTAINERS b/MAINTAINERS
index 1fd975c..00985c0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -877,6 +877,7 @@
 R:	Heinrich Schuchardt <xypron.glpk@gmx.de>
 S:	Maintained
 F:	cmd/rng.c
+F:	doc/api/rng.rst
 F:	drivers/rng/
 F:	drivers/virtio/virtio_rng.c
 F:	include/rng.h