bpf: Add BPF_MAP_TYPE_SK_STORAGE test to test_maps

This patch adds BPF_MAP_TYPE_SK_STORAGE test to test_maps.
The src file is rather long, so it is put into another dir map_tests/
and compile like the current prog_tests/ does.  Other existing
tests in test_maps can also be re-factored into map_tests/ in the
future.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/test_maps.h

@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _TEST_MAPS_H
+#define _TEST_MAPS_H
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#define CHECK(condition, tag, format...) ({				\
+	int __ret = !!(condition);					\
+	if (__ret) {							\
+		printf("%s(%d):FAIL:%s ", __func__, __LINE__, tag);	\
+		printf(format);						\
+		exit(-1);						\
+	}								\
+})
+
+#endif