perf trace: Beautify the 'level' argument of setsockopt

  # perf trace -e setsockopt
     0.000 ( 0.019 ms): systemd-resolv/1121 setsockopt(fd: 22, level: IP, optname: 50, optval: 0x7ffee2c0c134, optlen: 4) = 0
     0.022 ( 0.003 ms): systemd-resolv/1121 setsockopt(fd: 22, level: IP, optname: 11, optval: 0x7ffee2c0c114, optlen: 4) = 0
     0.027 ( 0.003 ms): systemd-resolv/1121 setsockopt(fd: 22, level: IP, optname: 8, optval: 0x7ffee2c0c134, optlen: 4) = 0
     0.032 ( 0.002 ms): systemd-resolv/1121 setsockopt(fd: 22, level: IP, optname: 10, optval: 0x7ffee2c0c134, optlen: 4) = 0
     0.036 ( 0.002 ms): systemd-resolv/1121 setsockopt(fd: 22, level: IP, optname: 25, optval: 0x7ffee2c0c114, optlen: 4) = 0
     0.043 ( 0.003 ms): systemd-resolv/1121 setsockopt(fd: 22, level: 1, optname: 62, optval: 0x7ffee2c0c0fc, optlen: 4) = 0
     0.055 ( 0.003 ms): systemd-resolv/1121 setsockopt(fd: 22, level: 1, optname: 25)
  ^C#

So the simple straight STRARRAY method is not enough as SOL_SOCKET is
'1' in most architectures but some use 0xffff (alpha, mips, parisc and
sparc), so a followup patch will create a specialized scnprintf to cover
that.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>