tracing: Fix C type errors in librados tracing

tracing: Fix C type errors in librados tracing

This fixes type errors like this:

In file included from /usr/include/lttng/tracepoint-event.h:69,
                 from …-build/include/tracing/librados.h:4143,
                 from …/src/tracing/librados.c:6
:
…-build/include/tracing/librados.h:
 In function ‘lttng_ust__event_probe__librados___rados_mon_command_exit’:
…-build/include/tracing/librados.h:477:9: error: initialization of ‘size_t’ {aka ‘long unsigned int’} from ‘size_t *’ {aka ‘long unsigned int *’} makes integer from pointer without a cast
  477 |         ceph_ctf_integerp(size_t, outslen, outslen)
      |         ^~~~~~~~~~~~~~~~~

GCC 14 will likely treat these type mismatches as an error
and fail the build.

Signed-off-by: Florian Weimer <fweimer@redhat.com>