ubifs: Convert ubifs to use the new mount API

Convert the ubifs filesystem to the new internal mount API as the old
one will be obsoleted and removed.  This allows greater flexibility in
communication of mount parameters between userspace, the VFS and the
filesystem.

See Documentation/filesystems/mount_api.txt for more information.

[sandeen: forward-port old patch, use dedicated context struct]]

Signed-off-by: David Howells <[email protected]>
Co-developed-by: Eric Sandeen <[email protected]>
Signed-off-by: Eric Sandeen <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Zhihao Cheng <[email protected]>
cc: Richard Weinberger <[email protected]>
cc: Zhihao Cheng <[email protected]>
cc: [email protected]
Signed-off-by: Christian Brauner <[email protected]>

Author: dhowells