Constifies hmcdrv_ftp_ops structures in s390's char
driver since they are not modified after their
initialization.

Detected and found using Coccinelle.
Suggested-by: NJulia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: NAya Mahfouz <mahfouz.saif.elyazal@gmail.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>