perf env: Remove env.h from other headers where just a fwd decl is needed

And fixup the fallout of c files not building due to now missing
headers.

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-sw8k3kpla98pr3rqypbjk9hf@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/mem2node.c

@@ -1,10 +1,12 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/compiler.h>
 #include <linux/bitmap.h>
+#include <linux/kernel.h>
 #include <linux/zalloc.h>
 #include <perf/cpumap.h>
 #include "cpumap.h"
 #include "debug.h"
+#include "env.h"
 #include "mem2node.h"
 #include "tests.h"