perf beauty sockaddr: Fix augmented syscall format warning

The sockaddr related examples given in
`tools/perf/examples/bpf/augmented_syscalls.c` almost always use `long`s
to represent most of their fields.

However, `size_t syscall_arg__scnprintf_sockaddr(..)` has a `scnprintf`
call that uses `"%#x"` as format string.

This throws a warning (whenever the syscall argument is `unsigned
long`).

Added `l` identifier to indicate that the `arg->value` is an unsigned
long.

Not sure about the complications of this with x86 though.

Signed-off-by: Cengiz Can <cengiz@kernel.wtf>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20200113174438.102975-1-cengiz@kernel.wtf
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>