bcachefs: 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/printbuf.c

@@ -56,6 +56,7 @@ void bch2_prt_vprintf(struct printbuf *out, const char *fmt, va_list args)
 
 		va_copy(args2, args);
 		len = vsnprintf(out->buf + out->pos, printbuf_remaining(out), fmt, args2);
+		va_end(args2);
 	} while (len + 1 >= printbuf_remaining(out) &&
 		 !bch2_printbuf_make_room(out, len + 1));