The completion did not check the interrupt status to see if any error
bits were asserted, check error bits and dump some registers if things
went wrong.

A few fixes are needed to make this work, the IXR_ERROR_FLAGS_MASK was
wrong, it included the done bits, which shows a bug in mask/unmask_irqs
which were using the wrong bits, simplify all of this stuff.

Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Reviewed-by: Moritz Fischer <moritz.fischer@ettus.com>
Acked-by: Alan Tull <atull@opensource.altera.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>