bcachefs: thread_with_file: Fix missing va_end()

Fixes: https://lore.kernel.org/linux-bcachefs/202402131603.E953E2CF@keescook/T/#u
Reported-by: coverity scan
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/thread_with_file.c

@@ -384,6 +384,8 @@ static ssize_t bch2_darray_vprintf(darray_char *out, gfp_t gfp, const char *fmt,
 
 		va_copy(args2, args);
 		len = vsnprintf(out->data + out->nr, darray_room(*out), fmt, args2);
+		va_end(args2);
+
 		if (len + 1 <= darray_room(*out)) {
 			out->nr += len;
 			return len;