When built with MSI support, the legacy domain reference was being
overwritten with MSI.

Create two separate domains for MSI and legacy interrupts.
Signed-off-by: Bharat Kumar Gogada <bharatku@xilinx.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Michal Simek <michal.simek@xilinx.com>