udf: Increase UDF_MAX_READ_VERSION to 0x0260

Some discs containing the UDF file system are unable to be mounted,
failing with the following message:

  UDF-fs: error (device sr0): udf_fill_super: minUDFReadRev=260
    (max is 250)

The UDF 2.60 specification [0] states in the section Basic Restrictions
& Requirements (page 10):

  The Minimum UDF Read Revision value shall be at most #0250 for all
  media with a UDF 2.60 file system. This indicates that a UDF 2.50
  implementation can read all UDF 2.60 media. Media that do not have a
  Metadata Partition may use a value lower than #250.

The conclusion is that the discs failing to mount were burned with a
faulty software, which didn't follow the specification. This can be
worked around by increasing UDF_MAX_READ_VERSION to 0x260, to match the
Minimum Read Revision. No other changes are required, as reading UDF
2.60 is backward compatible with UDF 2.50.

[0] http://www.osta.org/specs/pdf/udf260.pdf



Signed-off-by: Bartosz Taudul <wolf@nereid.pl>
Signed-off-by: Jan Kara <jack@suse.cz>