The dm_spi_ops.xfer() API does not support dual and quad SPI modes. It
also doesn't allow the zynqmp_gqspi driver to calculate the correct
number of dummy cycles for some NOR ops (as doing so also requires the
buswidth).
Port the zynqmp_gqspi driver to spi_controller_mem_ops, which gives us
the buswidth values to correctly support all SNOR_PROTO_X_X_X commands
and to properly calculate dummy cycles.