xilinx_spips: Update striping to be big-endian bit order

xilinx_spips: Update striping to be big-endian bit order

Update striping functionality to be big-endian bit order (as according to
the Zynq-7000 Technical Reference Manual). Output thereafter the even bits
into the flash memory connected to the lower QSPI bus and the odd bits into
the flash memory connected to the upper QSPI bus.

Signed-off-by: Francisco Iglesias <[email protected]>
Acked-by: Alistair Francis <[email protected]>
Reviewed-by: Edgar E. Iglesias <[email protected]>
Tested-by: Edgar E. Iglesias <[email protected]>
Message-id: 20171126231634[email protected]
Signed-off-by: Peter Maydell <[email protected]>