Fix build error for ecall

Change-Id: I019c8d22f30d6125d74ca1fd6e0107e02e517fe0
diff --git a/mbtk/libmbtk_lib/ril/mbtk_info_api.c b/mbtk/libmbtk_lib/ril/mbtk_info_api.c
index 1dc3464..222bcf1 100755
--- a/mbtk/libmbtk_lib/ril/mbtk_info_api.c
+++ b/mbtk/libmbtk_lib/ril/mbtk_info_api.c
@@ -2631,6 +2631,21 @@
     return 0;
 }
 
+int mbtk_ecall_state_change_cb_reg(mbtk_info_handle_t* handle, mbtk_info_callback_func cb)
+{
+    if(handle == NULL)
+    {
+        LOGE("ARG error.");
+        return -1;
+    }
+    if(info_item_process(handle, MBTK_INFO_ID_IND_ECALL_STATE_CHANGE, NULL, 0, NULL) < 0) {
+        return handle->info_err;
+    } else {
+        handle->ecall_state_cb = cb;
+        return 0;
+    }
+}
+
 
 int mbtk_get_modem_version(mbtk_info_handle_t* handle, void *modem_version)
 {
@@ -2648,3 +2663,4 @@
     }
 }
 
+