udf: Disallow R/W mode for disk with Metadata partition

Currently we do not support writing to UDF disks with Metadata partition.
There is already check that disks with declared minimal write revision to
UDF 2.50 or higher are mounted only in R/O mode but this does not cover
situation when minimal write revision is set incorrectly (e.g. to 2.01).

Link: https://lore.kernel.org/r/20200112144959.28104-1-pali.rohar@gmail.com


Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>