UDF: fix function name from udf_crc16 to udf_crc

We have to change udf_crc16() name to udf_crc() to be able to play with CRC
test.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Jan Kara <jack@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>