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: NBharat Kumar Gogada <bharatku@xilinx.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Acked-by: NMichal Simek <michal.simek@xilinx.com>