LU-9859 libcfs: use strim instead of cfs_trimwhite.

LU-9859 libcfs: use strim instead of cfs_trimwhite.

Linux lib provides identical functionality to cfs_trimwhite,
so discard that code and use the standard.

Linux-commit: 213b14b1fa55790f55b180ed5121b07f037c7ddd

Change-Id: Ide9d829aef554541a3dfb65ecb305e89c7ddf74a
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-on: https://review.whamcloud.com/34168
Reviewed-by: Ben Evans <bevans@cray.com>
Reviewed-by: Gu Zheng <gzheng@ddn.com>
Tested-by: Jenkins
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>