Kconfig files under arch/ directory are ignored by all_kconfigs(),
so include them for tags generation.

Link: http://lkml.kernel.org/r/1486206053-38223-1-git-send-email-houtao1@huawei.comSigned-off-by: Hou Tao <houtao1@huawei.com>
Cc: Michal Marek <mmarek@suse.com>
Cc: Joe Perches <joe@perches.com>
Cc: Mathieu Maret <mathieu.maret@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>