spi: zynqmp: gqspi: remove hardware settings from setup()

- This patch makes sure that there is no hardware settings
  during the transfer via setup()

- zynqmp_qspi_setup_transfer() call is moved inside function
  zynqmp_qspi_start_transfer()

Signed-off-by: Ranjit Waghmode <ranjit.waghmode@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>