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>