sf: winbond: Add Dual stacked and Dual parallel support

Added the Dual stacked and Dual parallel support for the
Winbond devices.

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>
sf: Add missing SPI_FLASH_U_PAGE flags in get_status

Added missed flag SPI_FLASH_U_PAGE in get_status call
for dual stacked mode

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>
spi: zynq_qspi: Fix the Rx FIFO overflow condition

Added the check for the Tx FIFO not empty condition
as well along with Rx FIFO not empty to get rid of
Rx FIFO overflow scenario.

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>