spl: Avoid checking for Ctrl-C in SPL with print_buffer()

We don't have a console in SPL so it doesn't make sense to check for
Ctrl-C when printing a memory dump. Skip this so that print_buffer() can
be used in SPL.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/lib/display_options.c b/lib/display_options.c
index cff20f3..ec16d75 100644
--- a/lib/display_options.c
+++ b/lib/display_options.c
@@ -205,8 +205,10 @@
 		addr += thislinelen * width;
 		count -= thislinelen;
 
+#ifndef CONFIG_SPL_BUILD
 		if (ctrlc())
 			return -1;
+#endif
 	}
 
 	return 0;