exfat: use truncate_inode_pages_final() at evict_inode()

Currently, exfat uses truncate_inode_pages() in exfat_evict_inode().
However, truncate_inode_pages() does not mark the mapping as exiting,
so reclaim may still install shadow entries for the mapping until
the inode teardown completes.

In older kernels like Linux 5.10, if shadow entries are present
at that point,clear_inode() can hit

BUG_ON(inode->i_data.nrexceptional);

To align with VFS eviction semantics and prevent this situation,
switch to truncate_inode_pages_final() in ->evict_inode().

Other filesystems were updated to use truncate_inode_pages_final()
in ->evict_inode() by commit 91b0abe36a7b ("mm + fs: store shadow
entries in page cache")'.

Signed-off-by: Yang Wen <anmuxixixi@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>