s390/qdio: clean up SIGA capability tracking

Don't bother with translating the SIGA-related capability bits into
our own internal format, just cache the full qdioac1 field instead.

Also adjust the helper macros so that they take a qdio_irq argument
and can be used everywhere, instead of taking a qdio_q and then
internally dereferencing the parent pointer.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>