Changed addr_range to use uint64.

I've tested this change on x86, causing no issues. I've checked over the code
for all other platforms and made the necessary changes and to the best of my
knowledge they should also still work, but I haven't actually built and
tested them. Once I've completed the kernel_args changes the other platforms
will need testing.

headers/private/kernel/boot/kernel_args.h

@@ -58,7 +58,7 @@ typedef struct kernel_args {
 	addr_range	cpu_kstack[MAX_BOOT_CPUS];
 
 	// boot volume KMessage data
-	void		*boot_volume;
+	uint64		boot_volume;
 	int32		boot_volume_size;
 
 	struct driver_settings_file *driver_settings;