libpayload: Enable colors in PDcurses

PDcurses wants set_blink to determine color count. Not exactly
obvious.

Change-Id: I8b2a32f0095d5900fa7e01f04f3f1d565dc2bedf
Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
Reviewed-on: http://review.coreboot.org/432
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

payloads/libpayload/curses/pdcurses-backend/pdcsetsc.c

@@ -28,5 +28,8 @@ int PDC_curs_set(int visibility)
 
 int PDC_set_blink(bool blinkon)
 {
+	if (pdc_color_started)
+		COLORS = 16;
+
 	return ERR;
 }