spi-zynq-qspi driver: prepare and unprepare functions aren´t present in lastest driver sources

[Iz4n32]

prepare and unprepare functions aren´t present despite of struct spi_controller still maintain this function pointers.

In latest kernel 5.15.X versions i saw an error when i use the "flashcp" command (from mtd-utils).
Under some special conditions accessing to the QSPI, i can see this error:

flashcp FILETOWRITTE /dev/mtd0
Erasing blocks: 1/1366 (0%)
While erasing blocks 0x00000000-0x00001000 on /dev/mtd0: Connection timed out

I can guarantee the correct writting under all conditions if i define, assign to the struct pointer and call prepare_transfer_hardware function before sending the message via qspi:
zynq_prepare_transfer_hardware;
zynq_unprepare_transfer_hardware;

I hope there is no problem in adding these routines againto this driver in the repository.

Thank you very much