perf memswap: Adopt 'struct u64_swap' from evsel.h

As it is not used in evsel.h and is a memory swap struct, so fits better
in memswap.h.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-wvzxu7a5l3m868ywwphrnnqo@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evsel.h

@@ -179,11 +179,6 @@ struct evsel {
 	} side_band;
 };
 
-union u64_swap {
-	u64 val64;
-	u32 val32[2];
-};
-
 struct perf_missing_features {
 	bool sample_id_all;
 	bool exclude_guest;

tools/perf/util/memswap.h

@@ -2,6 +2,13 @@
 #ifndef PERF_MEMSWAP_H_
 #define PERF_MEMSWAP_H_
 
+#include <linux/types.h>
+
+union u64_swap {
+	u64 val64;
+	u32 val32[2];
+};
+
 void mem_bswap_64(void *src, int byte_size);
 void mem_bswap_32(void *src, int byte_size);