tracing: Fix DECLARE_TRACE_CONDITION

Commit 287050d3 ("tracing: Add TRACE_EVENT_CONDITIONAL()") adds
macros to define conditional trace events (TRACE_EVENT_CONDITIONAL) and
tracepoints (DECLARE_TRACE_CONDITION), but sets up functionality for
direct use only for the former.

Add preprocessor bits in define_trace.h to allow usage of
DECLARE_TRACE_CONDITION just like DECLARE_TRACE.

Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/20250218123121.253551-2-gmonaco@redhat.com
Fixes: 287050d3 ("tracing: Add TRACE_EVENT_CONDITIONAL()")
Link: https://lore.kernel.org/linux-trace-kernel/20250128111926.303093-1-gmonaco@redhat.com


Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>