Kernel provides virtual IRQ number at teardown.  Get hwirq number from
virtual IRQ and clear correct MSI set bit.
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>