autoboot: Rework CONFIG_AUTOBOOT_STOP_STR_* usage

In order to not define a CONFIG value when the
CONFIG_AUTOBOOT_STOP_STR_* functionality is not enabled, rework the
assignment of empty and unused (as the code will be discarded under if
0, in the end) values to be AUTOBOOT_STOP_STR_* instead of
CONFIG_AUTOBOOT_STOP_STR_*.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/common/autoboot.c b/common/autoboot.c
index 848c33b..5d33199 100644
--- a/common/autoboot.c
+++ b/common/autoboot.c
@@ -40,11 +40,15 @@
 static int stored_bootdelay;
 static int menukey;
 
-#if !defined(CONFIG_AUTOBOOT_STOP_STR_CRYPT)
-#define CONFIG_AUTOBOOT_STOP_STR_CRYPT ""
+#if defined(CONFIG_AUTOBOOT_STOP_STR_CRYPT)
+#define AUTOBOOT_STOP_STR_CRYPT	CONFIG_AUTOBOOT_STOP_STR_CRYPT
+#else
+#define AUTOBOOT_STOP_STR_CRYPT	""
 #endif
-#if !defined(CONFIG_AUTOBOOT_STOP_STR_SHA256)
-#define CONFIG_AUTOBOOT_STOP_STR_SHA256 ""
+#if defined(CONFIG_AUTOBOOT_STOP_STR_SHA256)
+#define AUTOBOOT_STOP_STR_SHA256	CONFIG_AUTOBOOT_STOP_STR_SHA256
+#else
+#define AUTOBOOT_STOP_STR_SHA256	""
 #endif
 
 #ifdef CONFIG_AUTOBOOT_USE_MENUKEY
@@ -81,7 +85,7 @@
 	int err;
 
 	if (IS_ENABLED(CONFIG_AUTOBOOT_STOP_STR_ENABLE) && !crypt_env_str)
-		crypt_env_str = CONFIG_AUTOBOOT_STOP_STR_CRYPT;
+		crypt_env_str = AUTOBOOT_STOP_STR_CRYPT;
 
 	if (!crypt_env_str)
 		return 0;
@@ -160,7 +164,7 @@
 	int ret;
 
 	if (sha_env_str == NULL)
-		sha_env_str = CONFIG_AUTOBOOT_STOP_STR_SHA256;
+		sha_env_str = AUTOBOOT_STOP_STR_SHA256;
 
 	presskey = malloc_cache_aligned(DELAY_STOP_STR_MAX_LENGTH);
 	c = strstr(sha_env_str, ":");