Export libyang API "lyd_check_mandatory_tree" for Management framework (CVL) (#5714)

- Why I did it
Management framework (CVL) needs to call lyd_check_mandatory_tree() for validation and hence exported lyd_check_mandatory_tree() as an API.

- How I did it
Added "API" keyword before lyd_check_mandatory_tree() definition.

- How to verify it
There is no functionality code change here and no specific steps to verify it. Management framework (CVL) should be able to call this function and no patching and compilation error should be seen.

- Description for the changelog
Added "API" keyword before export lyd_check_mandatory_tree() function definition.

src/libyang/patch/libyang_mgmt_framework.patch

@@ -0,0 +1,13 @@
+diff --git a/src/tree_data.c b/src/tree_data.c
+index 04653a46..65dca211 100644
+--- a/src/tree_data.c
++++ b/src/tree_data.c
+@@ -842,7 +842,7 @@ error:
+     return ret;
+ }
+ 
+-int
++API int
+ lyd_check_mandatory_tree(struct lyd_node *root, struct ly_ctx *ctx, const struct lys_module **modules, int mod_count,
+                          int options)
+ {

src/libyang/patch/series

@@ -1,3 +1,4 @@
 libyang.patch
+libyang_mgmt_framework.patch
 swig.patch
 large_file_support_arm32.patch