radio: fixes in stub FM radio HAL.

Change-Id: I0adf39a08a364ffdecb1c7f618190174804865f4
diff --git a/modules/radio/radio_hal_tool.c b/modules/radio/radio_hal_tool.c
index 05d872e..6c40739 100644
--- a/modules/radio/radio_hal_tool.c
+++ b/modules/radio/radio_hal_tool.c
@@ -131,7 +131,7 @@
         radio_metadata_key_t key;
         radio_metadata_type_t type;
         void *value;
-        uint32_t size;
+        size_t size;
 
         radio_metadata_get_at_index(info.metadata, i, &key, &type, &value, &size);