sandbox: Support iotrace feature

Support the iotrace feature for sandbox, and enable it, using some dummy
I/O access methods.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/sandbox/include/asm/io.h

@@ -40,4 +40,14 @@ static inline void unmap_sysmem(const void *vaddr)
 /* Map from a pointer to our RAM buffer */
 phys_addr_t map_to_sysmem(const void *ptr);
 
+/* Define nops for sandbox I/O access */
+#define readb(addr) 0
+#define readw(addr) 0
+#define readl(addr) 0
+#define writeb(v, addr)
+#define writew(v, addr)
+#define writel(v, addr)
+
+#include <iotrace.h>
+
 #endif

include/configs/sandbox.h

@@ -16,6 +16,9 @@
 
 #endif
 
+#define CONFIG_IO_TRACE
+#define CONFIG_CMD_IOTRACE
+
 #define CONFIG_SYS_TIMER_RATE		1000000
 
 #define CONFIG_BOOTSTAGE