sandbox: Switch over to generic board

Add generic board support for sandbox. and remove the old board init code.

Select CONFIG_SYS_GENERIC_BOARD for sandbox now that this is supported.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@ti.com>
diff --git a/arch/sandbox/include/asm/io.h b/arch/sandbox/include/asm/io.h
index 54051a3..0c022f1 100644
--- a/arch/sandbox/include/asm/io.h
+++ b/arch/sandbox/include/asm/io.h
@@ -20,6 +20,9 @@
  * MA 02111-1307 USA
  */
 
+#ifndef __SANDBOX_ASM_IO_H
+#define __SANDBOX_ASM_IO_H
+
 /*
  * Given a physical address and a length, return a virtual address
  * that can be used to access the memory range with the caching
@@ -52,3 +55,5 @@
 
 /* Map from a pointer to our RAM buffer */
 phys_addr_t map_to_sysmem(void *ptr);
+
+#endif