fs/libfs: don't assume blocksize <= PAGE_SIZE in generic_check_addressable

fs/libfs: don't assume blocksize <= PAGE_SIZE in generic_check_addressable

Since [1], it is possible for filesystems to have blocksize > PAGE_SIZE
of the system.

Remove the assumption and make the check generic for all blocksizes in
generic_check_addressable().

[1] https://lore.kernel.org/linux-xfs/20240822135018.1931258-1-kernel@pankajraghav.com/

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
Link: https://lore.kernel.org/20250630104018.213985-1-p.raghav@samsung.com
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Baokun Li <libaokun1@huawei.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>