net: pktgen: fix code style (WARNING: macros should not use a trailing semicolon)

net: pktgen: fix code style (WARNING: macros should not use a trailing semicolon)

Fix checkpatch code style warnings:

  WARNING: macros should not use a trailing semicolon
  #180: FILE: net/core/pktgen.c:180:
  +#define func_enter() pr_debug("entering %s\n", __func__);

  WARNING: macros should not use a trailing semicolon
  #234: FILE: net/core/pktgen.c:234:
  +#define   if_lock(t)           mutex_lock(&(t->if_lock));

  CHECK: Unnecessary parentheses around t->if_lock
  #235: FILE: net/core/pktgen.c:235:
  +#define   if_unlock(t)           mutex_unlock(&(t->if_lock));

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>