xilinx_spips: Inhibit interrupts in LQSPI mode

xilinx_spips: Inhibit interrupts in LQSPI mode

The real hardware does not produce interrupts in LQSPI mode. Inhibit
generation of interrupts when the LQ_MODE bit is set.

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>
Message-id: dff794a06872009ea7e5733ce6adcff94d18bbd0.1369117359.git.peter.crosthwaite@xilinx.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>