xilinx_spips: lqspi: Dont touch config register

The LQSPI mode is supposed to work via the automatic CS mode feature
rather than manipulate CS lines itself. Now that auto CS is implemented
remove LQSPIs CS mode override logic. There is still a need to
manipulate the U_PAGE bit in LQSPI config register to implement
dual-stack mode however.

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: 000c8dd54df09523f17052638100722ef0f5a3af.1369117359.git.peter.crosthwaite@xilinx.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
