LU-13199 lustre: remove cl_{offset,index,page_size} helpers

LU-13199 lustre: remove cl_{offset,index,page_size} helpers

These helpers could be replaced with PAGE_SIZE and PAGE_SHIFT calculation
directly which avoid CPU overhead.

Change-Id: I624136d4399a03e599f09f00a77b86de045f19e9
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/37426
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>