spi: rzv2m-csi: Adopt HZ_PER_MHZ for max spi clock

Make use of HZ_PER_MHZ for CSI_MAX_SPI_SCKO to make it clear
what its value means.
Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20230715010407.1751715-3-fabrizio.castro.jz@renesas.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-rzv2m-csi.c

@@ -13,6 +13,7 @@
 #include <linux/platform_device.h>
 #include <linux/reset.h>
 #include <linux/spi/spi.h>
+#include <linux/units.h>
 
 /* Registers */
 #define CSI_MODE		0x00	/* CSI mode control */
@@ -71,7 +72,7 @@
 #define TX_TIMEOUT_ERROR	BIT(2)
 #define RX_TIMEOUT_ERROR	BIT(3)
 
-#define CSI_MAX_SPI_SCKO	8000000
+#define CSI_MAX_SPI_SCKO	(8 * HZ_PER_MHZ)
 
 struct rzv2m_csi_priv {
 	void __iomem *base;