fs/udf: re-use hex_asc_upper_{hi,lo} macros

This patch cleans up udf_translate_to_linux() a bit by using globally defined
macros instead of custom code.

We can use sprintf(buf, "%04X", ...) there as well, but this one faster.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>