udf: Remove declarations of arrays of size UDF_NAME_LEN (256 bytes)

There are several places in UDF where we declared temporary arrays of
UDF_NAME_LEN bytes on stack. This is not nice to stack usage so this patch
changes those places to use kmalloc() instead. Also clean up bail-out paths
in those functions when we are changing them.

Signed-off-by: Jan Kara <jack@suse.cz>