lsfd: fill ENDPOINTS column for eventfd

lsfd: fill ENDPOINTS column for eventfd

An example output:

  $ ./lsfd -Q '(TYPE == "eventfd") and (ENDPOINTS =~ ".+") ' -o+ENDPOINTS
  COMMAND          PID USER ASSOC MODE    TYPE       SOURCE MNTID INODE NAME   ENDPOINTS
  pipewire       17251  jet    40  rw- eventfd anon_inodefs    15  1060 id=818 17255,pipewire-pulse,26
  pipewire       17251  jet    52  rw- eventfd anon_inodefs    15  1060 id=695 17255,pipewire-pulse,30
									       17255,pipewire-pulse,37
									       17255,pipewire-pulse,49
  pipewire       17251  jet    54  rw- eventfd anon_inodefs    15  1060 id=845 17255,pipewire-pulse,31
  pipewire       17251  jet    61  rw- eventfd anon_inodefs    15  1060 id=212 17255,pipewire-pulse,45
  pipewire       17251  jet    62  rw- eventfd anon_inodefs    15  1060 id=224 17255,pipewire-pulse,46
  pipewire-pulse 17255  jet    26  rw- eventfd anon_inodefs    15  1060 id=818 17251,pipewire,40
  pipewire-pulse 17255  jet    30  rw- eventfd anon_inodefs    15  1060 id=695 17251,pipewire,52
									       17255,pipewire-pulse,37
									       17255,pipewire-pulse,49
  pipewire-pulse 17255  jet    31  rw- eventfd anon_inodefs    15  1060 id=845 17251,pipewire,54
  pipewire-pulse 17255  jet    37  rw- eventfd anon_inodefs    15  1060 id=695 17251,pipewire,52
									       17255,pipewire-pulse,30
									       17255,pipewire-pulse,49
  pipewire-pulse 17255  jet    45  rw- eventfd anon_inodefs    15  1060 id=212 17251,pipewire,61
  pipewire-pulse 17255  jet    46  rw- eventfd anon_inodefs    15  1060 id=224 17251,pipewire,62
  pipewire-pulse 17255  jet    49  rw- eventfd anon_inodefs    15  1060 id=695 17251,pipewire,52
									       17255,pipewire-pulse,30
									       17255,pipewire-pulse,37

Signed-off-by: Masatake YAMATO <yamato@redhat.com>