soundwire: cdns: Fix compilation error on arm64

On arm64 the cadence_master.c file doesn't compile.

readl and writel are undefined.
This patch fixes that by including io.h.

Signed-off-by: Jan Kotas <jank@cadence.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/soundwire/cadence_master.c

@@ -9,6 +9,7 @@
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/interrupt.h>
+#include <linux/io.h>
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
 #include <linux/soundwire/sdw_registers.h>