Add QSPI driver code for the Microchip PolarFire SoC. This driver supports the QSPI standard, dual and quad mode interfaces. Co-developed-by: Naga Sureshkumar Relli <nagasuresh.relli@microchip.com> Signed-off-by: Naga Sureshkumar Relli <nagasuresh.relli@microchip.com> Signed-off-by: Padmarao Begari <padmarao.begari@microchip.com> Reviewed-by: Conor Dooley <conor.dooley@microchip.com>