perf trace: Introduce syscall_arg__scnprintf_strarray_flags

perf trace: Introduce syscall_arg__scnprintf_strarray_flags

So that one can just define a strarray and process it as a set of flags,
similar to syscall_arg__scnprintf_strarray() with plain arrays.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-nnt25wkpkow2w0yefhi6sb7q@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>