sandbox: Drop ad-hoc device declarations in SPL

Since sandbox's SPL is build with of-platadata, we should not use
U_BOOT_DEVICE() declarations as well. Drop them.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/sysreset/sysreset_sandbox.c b/drivers/sysreset/sysreset_sandbox.c
index 69c22a7..71cabd1 100644
--- a/drivers/sysreset/sysreset_sandbox.c
+++ b/drivers/sysreset/sysreset_sandbox.c
@@ -130,7 +130,9 @@
 	.ops		= &sandbox_warm_sysreset_ops,
 };
 
+#if !CONFIG_IS_ENABLED(OF_PLATDATA)
 /* This is here in case we don't have a device tree */
 U_BOOT_DEVICE(sysreset_sandbox_non_fdt) = {
 	.name = "sysreset_sandbox",
 };
+#endif