sandbox: fix 64bit build

On x86_64 we need CONFIG_PHYS_ADDR_T_64BIT to make the resource sizes
64bit. The kernel has this as a Kconfig variable, but on barebox sandbox
will build with whatever compiler we find, so we can't put it into Kconfig.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arch/sandbox/include/asm/types.h

@@ -7,6 +7,13 @@
  * 64 bit
  */
 #define INTERNAL_SIZE_T unsigned long
+
+/*
+ * This is a Kconfig variable in the Kernel, but we want to detect
+ * this during compile time, so we set it here.
+ */
+#define CONFIG_PHYS_ADDR_T_64BIT
+
 #endif
 
 typedef unsigned short umode_t;