The ACK of an inexistent IRQ can trigger an spurious IRQ that breaks the
txrx logic. This has been observed on axi_quad_spi:3.2 core.
This patch only ACKs IRQs that have not been Acknowledge jet.
Reported-by: Edward Kigwana <ekigwana@scires.com> Tested-by: Edward Kigwana <ekigwana@scires.com> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com> Signed-off-by: Mark Brown <broonie@kernel.org> Cc: stable@vger.kernel.org