xilinx_spips: Fix striping behaviour

xilinx_spips: Fix striping behaviour

The QSPI controller was using byte-wide stripes when striping across
the two flashes in dual parallel mode. The real hardware however uses
individual bit striping. QEMU misbehaves in the (corner) case where
data is written/read in dual-parallel mode and read/written back in
single mode.

Signed-off-by: Peter Crosthwaite <[email protected]>
Reviewed-by: Peter Maydell <[email protected]>
Reviewed-by: Edgar E. Iglesias <[email protected]>
Message-id: 718a61df1bf746ec06f6da44d12f8317af7b08ce.1369117359[email protected]
Signed-off-by: Peter Maydell <[email protected]>