LU-16515 clio: Remove cl_page_size()

LU-16515 clio: Remove cl_page_size()

cl_page_size() is just a function which does:
1 << PAGE_SHIFT

and the kernel provides a macro for that - PAGE_SIZE.
Maybe it didn't when this function was added, but it sure
does now.

So, remove cl_page_size().

Test-parameters: trivial
Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: I6c27f6db7cfec5d9054aab95beccffe3c2da02bb
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/49918
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>