kernel-doc: Fix example in Nested structs/unions

Add missing ';' as well as fixes the indent for the first struct.
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Link: https://lore.kernel.org/r/20201207210027.1049346-1-ben.widawsky@intel.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/doc-guide/kernel-doc.rst

@@ -247,12 +247,12 @@ It is possible to document nested structs and unions, like::
           struct {
             int memb1;
             int memb2;
-        }
+          };
           struct {
             void *memb3;
             int memb4;
-          }
-        }
+          };
+        };
         union {
           struct {
             int memb1;