xilinx: versal: Define CONFIG_CQSPI_REF_CLK

With commit 55b3ba4c ("spi: cadence_qspi: Migrate CONFIG_CQSPI_REF_CLK
to Kconfig") CONFIG_CQSPI_REF_CLK is moved to Kconfig.

The static value via Kconfig is a fallback option in case of clock
framework is not enabled or fails for some reason.

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/fe7c38a19e878c307d5b75311bbfd8cf6c1f601e.1659691195.git.michal.simek@amd.com