LU-13258 libcfs: fixes for cfs_arch_init()

LU-13258 libcfs: fixes for cfs_arch_init()

The introduction of cfs_arch_init() brought two problems.

1/ wait_bit_init() wasn't known due to a missing include file.
2/ cfs_arch_init() was not marked __init, but it called
   a function (wait_bit_init) that was.

This patch fixes both of these.

Fixes: 3453c95f513c ("LU-13258 libcfs: make apply_workqueue_attrs() available for Lustre")
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I6f19e11e68f52ca8071332364d369ed3a717d5c9
Reviewed-on: https://review.whamcloud.com/37727
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>