sandbox: move sandbox specifics to booti_setup()

Instead of checking a configuration setting in booti_start() adjust the
sandbox implementation of booti_setup().

Write a console message when trying to run the booti command on the sandbox
indicating that it is not supported.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/arch/sandbox/lib/bootm.c b/arch/sandbox/lib/bootm.c
index 8dbcd9f..44ba8b5 100644
--- a/arch/sandbox/lib/bootm.c
+++ b/arch/sandbox/lib/bootm.c
@@ -85,5 +85,7 @@
 int booti_setup(ulong image, ulong *relocated_addr, ulong *size,
 		bool force_reloc)
 {
-	return 0;
+	log_err("Booting is not supported on the sandbox.\n");
+
+	return 1;
 }
diff --git a/cmd/booti.c b/cmd/booti.c
index 898df0f..b9637b3 100644
--- a/cmd/booti.c
+++ b/cmd/booti.c
@@ -74,7 +74,7 @@
 	unmap_sysmem((void *)ld);
 
 	ret = booti_setup(ld, &relocated_addr, &image_size, false);
-	if (ret || IS_ENABLED(CONFIG_SANDBOX))
+	if (ret)
 		return 1;
 
 	/* Handle BOOTM_STATE_LOADOS */