perf symbols: Include elf.h header regardless LIBELF_SUPPORT

The elf.h header file is used for NO_LIBELF build too so it should be
included anyway.  Also remove duplicated include of the header file in
symbol-*.c.  This patch fixes following build error on NO_LIBELF build:

    CC tests/hists_link.o
tests/hists_link.c: In function ‘setup_fake_machine’:
tests/hists_link.c:132:8: error: ‘STB_GLOBAL’ undeclared (first use in this function)
tests/hists_link.c:132:8: note: each undeclared identifier is reported only once for each function it appears in
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1356679009-32122-1-git-send-email-namhyung@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/symbol-elf.c

-#include <libelf.h>
-#include <gelf.h>
-#include <elf.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <errno.h>

tools/perf/util/symbol-minimal.c

 #include "symbol.h"
 
-#include <elf.h>
 #include <stdio.h>
 #include <fcntl.h>
 #include <string.h>

tools/perf/util/symbol.h

@@ -16,8 +16,8 @@
 #ifdef LIBELF_SUPPORT
 #include <libelf.h>
 #include <gelf.h>
-#include <elf.h>
 #endif
+#include <elf.h>
 
 #include "dso.h"