cmd_mtdparts.c: allow to omit definitions for default settings

There is actually no good reason to enforce that all board
configuations must define default settings for "mtdids" and
"mtdparts".  Actually this may be difficult to handle, especially on
boards where different sizes of flash chips can be fit, so there is no
real "default" partition map for all boards.

Lift this arbitrary limitation.
Signed-off-by: NWolfgang Denk <wd@denx.de>

common/cmd_mtdparts.c

@@ -137,14 +137,12 @@
 #if defined(MTDIDS_DEFAULT)
 static const char *const mtdids_default = MTDIDS_DEFAULT;
 #else
-#warning "MTDIDS_DEFAULT not defined!"
 static const char *const mtdids_default = NULL;
 #endif
 
 #if defined(MTDPARTS_DEFAULT)
 static const char *const mtdparts_default = MTDPARTS_DEFAULT;
 #else
-#warning "MTDPARTS_DEFAULT not defined!"
 static const char *const mtdparts_default = NULL;
 #endif
 
@@ -1264,8 +1262,10 @@ static void list_partitions(void)
 	}
 
 	printf("\ndefaults:\n");
-	printf("mtdids  : %s\n", mtdids_default);
-	printf("mtdparts: %s\n", mtdparts_default);
+	printf("mtdids  : %s\n",
+		mtdids_default ? mtdids_default : "none");
+	printf("mtdparts: %s\n",
+		mtdparts_default ? mtdparts_default : "none");
 }
 
 /**