Fix: use of uninitialized ret value in lttng_abi_create_event

Fix: use of uninitialized ret value in lttng_abi_create_event

Fixes the following compiler warning:

/home/jenkins/workspace/lttng-modules_VERSION_param-build/arch/x86-32/src/lttng-modules/lttng-abi.c: In function ‘lttng_abi_create_event’:
/home/jenkins/workspace/lttng-modules_VERSION_param-build/arch/x86-32/src/lttng-modules/lttng-abi.c:987:16: warning: ‘ret’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  int event_fd, ret;

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>