spi: zynqmp_gqspi: Add support for ZynqMP qspi driver

This patch adds qspi driver support for ZynqMP SoC. This
driver is responsible for communicating with qspi flash
devices.

Signed-off-by: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
[jagan: removed GQSPI_MIO_NUM_ macros]
Reviewed-by: Jagan Teki <jagan@openedev.com>