Add missing definition for read_barries_depends() for h8300 to fix error:
kernel/task_work.c: In function 'task_work_cancel':
kernel/task_work.c:38:3: error: implicit declaration of function 'read_barrier_depends' [-Werror=implicit-function-declaration]
cc1: some warnings being treated as errors
make[1]: *** [kernel/task_work.o] Error 1
make: *** [kernel] Error 2

Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: David Howells <dhowells@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Jiang Liu <jiang.liu@huawei.com>