LU-14195 llite: add force_uaccess_{begin,end} helpers

LU-14195 llite: add force_uaccess_{begin,end} helpers

Linux kernel version 5.10 adds force_uaccess_begin() and
force_uaccess_end() helpers to wrap get_fs() and set_fs()
for undoing any damange done by set_fs(KERNEL_DS).

Lustre-change: https://review.whamcloud.com/44165
Lustre-commit: TBD (from 597a8a1e0c4c09b86b7d4e860cdcd6a3fedcb6dc)

Fixes: a84af70dcab ("LU-12358 pcc: add project quota support on PCC backend")
Change-Id: I68745a8a1e26312ffe6ee8388f962b9c834df97b
Signed-off-by: Jian Yu <yujian@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/44160
Reviewed-by: Yingjin Qian <qian@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Li Xi <lixi@ddn.com>