tracing: Cleanup upper_empty() in pid_list

Instead of find_first_bit() use the dedicated bitmap_empty(),
and make upper_empty() a nice one-liner.

While there, fix opencoded BITS_PER_TYPE().

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20250429195119.620204-1-yury.norov@gmail.com
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Author: YuryNorov

kernel/trace/pid_list.c

@@ -81,13 +81,9 @@ static inline bool upper_empty(union upper_chunk *chunk)
 {
 	/*
 	 * If chunk->data has no lower chunks, it will be the same
-	 * as a zeroed bitmask. Use find_first_bit() to test it
-	 * and if it doesn't find any bits set, then the array
-	 * is empty.
+	 * as a zeroed bitmask.
 	 */
-	int bit = find_first_bit((unsigned long *)chunk->data,
-				 sizeof(chunk->data) * 8);
-	return bit >= sizeof(chunk->data) * 8;
+	return bitmap_empty((unsigned long *)chunk->data, BITS_PER_TYPE(chunk->data));
 }
 
 static inline int pid_split(unsigned int pid, unsigned int *upper1,