s390/hmcdrv: HMC drive CD/DVD access

This device driver allows accessing a HMC drive CD/DVD-ROM.
It can be used in a LPAR and z/VM environment.

Reviewed-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Ralf Hoppe <rhoppe@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>