spi: cadence_qspi: support DM_CLK

Support loading clk speed via DM instead of requiring ad-hoc code.

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
diff --git a/drivers/spi/cadence_qspi.h b/drivers/spi/cadence_qspi.h
index 20cceca..99dee75 100644
--- a/drivers/spi/cadence_qspi.h
+++ b/drivers/spi/cadence_qspi.h
@@ -16,6 +16,7 @@
 #define CQSPI_READ_CAPTURE_MAX_DELAY	16
 
 struct cadence_spi_platdata {
+	unsigned int	ref_clk_hz;
 	unsigned int	max_hz;
 	void		*regbase;
 	void		*ahbbase;