spi: cadence_qspi: Ensure spi_calibration is run when sclk change

Ensuring spi_calibration is run when there is a change of sclk
frequency. This will ensure the qspi flash access works for high
sclk frequency

Signed-off-by: Chin Liang See <clsee@altera.com>
Cc: Dinh Nguyen <dinguyen@opensource.altera.com>
Cc: Dinh Nguyen <dinh.linux@gmail.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Stefan Roese <sr@denx.de>
Cc: Vikas Manocha <vikas.manocha@st.com>
Cc: Jagannadh Teki <jteki@openedev.com>
Cc: Pavel Machek <pavel@denx.de>
Acked-by: Marek Vasut <marex@denx.de>
Reviewed-by: Jagan Teki <jteki@openedev.com>
diff --git a/drivers/spi/cadence_qspi.h b/drivers/spi/cadence_qspi.h
index 98e57aa..2912e36 100644
--- a/drivers/spi/cadence_qspi.h
+++ b/drivers/spi/cadence_qspi.h
@@ -38,6 +38,7 @@
 	int		qspi_is_init;
 	unsigned int	qspi_calibrated_hz;
 	unsigned int	qspi_calibrated_cs;
+	unsigned int	previous_hz;
 };
 
 /* Functions call declaration */