drivers: s390/cio: Fix compilation warning about const qualifiers

Update __ccwdev_check_busid() and __ccwgroupdev_check_busid() to use
"const" qualifiers to fix the compiler warning.

Reported-by: kbuild test robot <lkp@intel.com>
Cc: gregkh@linuxfoundation.org
Cc: devel@driverdev.osuosl.org
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>