s390/dasd: Remove old defines and function

Commit 4d284cac

 ("[S390] Avoid excessive inlining.") removed
bytes_per_record() which was the only user of the defines ECKD_C0 and
ECKD_F*, and round_up_multiple(). Let's get rid of those.

Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>