When dispatching memory access to PCI BAR region, we must
look for possible subregions, used by the PCI device to map
different memory areas inside the same PCI BAR.

Since the data offset we received is calculated starting at the
region start address we need to adjust the offset for the subregion.

The data offset inside the subregion is calculated by substracting
the subregion's starting address from the data offset in the region.

The access to the MSIX region is now handled in a generic way,
we do not need the specific trap_msix() function anymore.
Signed-off-by: NPierre Morel <pmorel@linux.vnet.ibm.com>
Reviewed-by: NYi Min Zhao <zyimin@linux.vnet.ibm.com>
Message-Id: <1512046530-17773-8-git-send-email-pmorel@linux.vnet.ibm.com>
Signed-off-by: NCornelia Huck <cohuck@redhat.com>