spl: Change debug to printf for "Unsupported boot-device"

We had the problem on an AM33xx platform, that SPL detected an
unsupported boot-device. But since this message is a debug message
it took a bit of time to really know, where the hangup in SPL
resulted from. So let's change this debug message to a printf
and also print the detected boot-device that is not supported.
This makes debugging of such cases much easier.
Signed-off-by: NStefan Roese <sr@denx.de>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Tom Rini <trini@ti.com>
Acked-by: NHeiko Schocher <hs@denx.de>

common/spl/spl.c

@@ -221,7 +221,9 @@ void board_init_r(gd_t *dummy1, ulong dummy2)
 		break;
 #endif
 	default:
-		debug("SPL: Un-supported Boot Device\n");
+#if defined(CONFIG_SPL_SERIAL_SUPPORT) && defined(CONFIG_SPL_LIBCOMMON_SUPPORT)
+		printf("SPL: Unsupported Boot Device %d\n", boot_device);
+#endif
 		hang();
 	}