22dd1ac9 ("tools: Remove feature-libelf-mmap feature detection")
correctly simplified the this feature detection, but forgot to remove
the call to the removed function in the main() function for the
test-all.c fast path feature detection, making it fail and thus do all
the feature detection individually, fix it.

  $ cat /tmp/build/perf/feature/test-all.make.output
  test-all.c: In function ‘main’:
  test-all.c:188:2: error: implicit declaration of function ‘main_test_libelf_mmap’; did you mean ‘main_test_libelf’? [-Werror=implicit-function-declaration]
    188 |  main_test_libelf_mmap();
        |  ^~~~~~~~~~~~~~~~~~~~~
        |  main_test_libelf
  cc1: all warnings being treated as errors
  $ vim tools/build/feature/test-all.c
  $ rm -rf /tmp/build/perf ; mkdir -p /tmp/build/perf ;make V=1 -k O=/tmp/build/perf  -C tools/perf install-bin ; perf test python
  <SNIP>
  $ cat /tmp/build/perf/feature/test-all.make.output
  $

Fixes: 22dd1ac9 ("tools: Remove feature-libelf-mmap feature detection")
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>