s390/hmcdrv: Remove commented out code

s390/hmcdrv: Remove commented out code

The create_class() api is retiring in favor of class_register() (see:
https://lore.kernel.org/all/2023040244-duffel-pushpin-f738@gregkh/).
The HMCDRV_DEV_CLASS define is hiding a use of create_class(), but it is
permanently disabled as it is commented out. To avoid supporting code
that is disabled, the suggestion is to remove all code hiding be behind
any #ifdef HMCDRV_DEV_CLASS.

Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20260308103255.757461-1-jkoolstra@xs4all.nl
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>