tegra20: display: fix checking of return value

The calling code seems a bit in doubt about the return value of fdtdec_lookup_phandle. Since it returns a negative value on error (and fdt_node_offset_by_phandle as well), check for that.

---

arch/arm/cpu/armv7/tegra20/display.c:331:26: warning: comparison of constant 0 with boolean expression is always false [-Wtautological-constant-out-of-range-compare]

        if (!config->panel_node < 0) {
            ~~~~~~~~~~~~~~~~~~~ ^ ~

NOT tested on hw.

---
 arch/arm/cpu/armv7/tegra20/display.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 488f0c6..fd77f3f 100644
@@ -328,7 +328,7 @@ static int tegra_display_decode_config(const void *blob,
 	rgb = fdt_subnode_offset(blob, node, "rgb");
 
 	config->panel_node = fdtdec_lookup_phandle(blob, rgb, "nvidia,panel");
-	if (!config->panel_node < 0) {
+	if (config->panel_node < 0) {
 		debug("%s: Cannot find panel information\n", __func__);
 		return -1;
 	}

1.8.3.2

(On Seaboard/Springbank; booted via tegrarcm and the LCD still works)