ntfs: change mft_no type to u64
Changes the type of ntfs_inode::mft_no from unsigned long to u64
to safely handle the full 48-bit range without truncation risk, especially
in preparation for broader VFS inode number type (i_ino:u64) and to
improve consistency with ntfs driver practices.
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>