dev: gcdb: Fix bug in passing of boot argument

Bug is in previous gerrit preventing the panel name
from being passed from the LK to the kernel.

Change-Id: Idbb0bd8daf0eb974863d7d97b2331d350dc6aa60
diff --git a/dev/gcdb/display/gcdb_display.c b/dev/gcdb/display/gcdb_display.c
index c184b11..e7f11f3 100755
--- a/dev/gcdb/display/gcdb_display.c
+++ b/dev/gcdb/display/gcdb_display.c
@@ -180,8 +180,8 @@
 
 	if (buf_size < (strlen(panel_node) + dsi_id_len +
 			MAX_PANEL_FORMAT_STRING + 1) ||
-		strlen(panel_node) ||
-		strlen(dsi_id))
+		!strlen(panel_node) ||
+		!strlen(dsi_id))
 	{
 		ret = false;
 	}