s390/cio: sanitize css_general_characteristics definition

Change css_general_characteristics such that the bitfields don't
straddle storage-unit boundaries of the base types.

This does not change the offsets of the structs members but now
we do as documented and also fix the following sparse complaint:
drivers/s390/cio/chsc.c:926:56:
	warning: invalid access past the end of 'css_general_characteristics' (16 18)

Signed-off-by: Sebastian Ott <sebott@linux.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>