doc: add system reset to API documentation

Complete the Sphinx documentation in include/sysreset.h
Add the include to the generated HTML documentation of the U-Boot API.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/doc/api/sysreset.rst b/doc/api/sysreset.rst
new file mode 100644
index 0000000..a51b06c
--- /dev/null
+++ b/doc/api/sysreset.rst
@@ -0,0 +1,7 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+System reset
+============
+
+.. kernel-doc:: include/sysreset.h
+   :internal: