mm/memfd_luo: use i_size_write() to set inode size during retrieve

mm/memfd_luo: use i_size_write() to set inode size during retrieve

Use i_size_write() instead of directly assigning to inode->i_size when
restoring the memfd size in memfd_luo_retrieve(), to keep code
consistency.

No functional change intended.

Link: https://lore.kernel.org/20260326084727.118437-5-duanchenghao@kylinos.cn
Signed-off-by: Chenghao Duan <duanchenghao@kylinos.cn>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Haoran Jiang <jianghaoran@kylinos.cn>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Pratyush Yadav <pratyush@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>