t132: Replace fallback with CONFIG_CBFS_PREFIX

Use the Kconfig value to load the name of the stage instead of the
hard-coded fallback stage.

(cherry picked from commit de4310af6f6dbeedd7432683d1d1fe12ce48f46e)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: I1ac707efe38e29f109dbbe206de74fbfe7cb7b0b
Reviewed-on: http://review.coreboot.org/8576
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Aaron Durbin <adurbin@google.com>

src/soc/nvidia/tegra132/bootblock.c

@@ -68,7 +68,8 @@ void main(void)
 
 	printk(BIOS_INFO, "T132 bootblock: Mainboard bootblock init done\n");
 
-	entry = cbfs_load_stage(CBFS_DEFAULT_MEDIA, "fallback/romstage");
+	entry = cbfs_load_stage(CBFS_DEFAULT_MEDIA,
+				CONFIG_CBFS_PREFIX "/romstage");
 
 	if (entry) {
 		printk(BIOS_INFO, "T132 bootblock: jumping to romstage\n");

src/soc/nvidia/tegra132/romstage.c

@@ -40,6 +40,7 @@ void main(void)
 
 	while (1);
 
-	entry = cbfs_load_stage(CBFS_DEFAULT_MEDIA, "fallback/ramstage");
+	entry = cbfs_load_stage(CBFS_DEFAULT_MEDIA,
+				CONFIG_CBFS_PREFIX "/ramstage");
 	stage_exit(entry);
 }