doc: api: bootcount: Convert to rST documentation

Move to the new documentation style with rST formatting.

Signed-off-by: Vasileios Amoiridis <vasileios.amoiridis@cern.ch>
diff --git a/doc/api/index.rst b/doc/api/index.rst
index 51b2013..ec0b8ad 100644
--- a/doc/api/index.rst
+++ b/doc/api/index.rst
@@ -6,6 +6,7 @@
 .. toctree::
    :maxdepth: 2
 
+   bootcount
    clk
    dfu
    dm