kunit: remove unused structure definition

remove unused string_stream_alloc_context structure definition.
Signed-off-by: YoungJun.park <her0gyugyu@gmail.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

lib/kunit/string-stream.c

@@ -131,11 +131,6 @@ bool string_stream_is_empty(struct string_stream *stream)
 	return list_empty(&stream->fragments);
 }
 
-struct string_stream_alloc_context {
-	struct kunit *test;
-	gfp_t gfp;
-};
-
 struct string_stream *alloc_string_stream(struct kunit *test, gfp_t gfp)
 {
 	struct string_stream *stream;