PNPACPI: extend irq_flags() to set IORESOURCE_IRQ_SHAREABLE when appropriate

This simplifies IRQ resource parsing slightly by computing all the
IORESOURCE_IRQ_* flags at the same time.

This also keeps track of shareability information when parsing options
from _PRS.  Previously we ignored shareability in _PRS.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Acked-By: Rene Herman <rene.herman@gmail.com>
Signed-off-by: Len Brown <len.brown@intel.com>