drivers: spi: cadence: set cqspi to the driver_data field of struct device

When initialize cadence qspi controller, it is need to set cqspi
to the driver_data field of struct device, because it will be
used in function cqspi_remove/suspend/resume(). Otherwise, there
will be a crash trace as below when invoking these finctions.
Call trace:
 cqspi_suspend+0x14/0x44
 dpm_run_callback+0x50/0x1c0
 __device_suspend+0x114/0x514
 ......
 el0_svc+0x20/0x30
 el0_sync_handler+0x1a4/0x1b0
 el0_sync+0x174/0x180

Fixes: 31fb632b("spi: Move cadence-quadspi driver to drivers/spi/")
Cc: stable@vger.kernel.org
Signed-off-by: Meng Li <Meng.Li@windriver.com>