video: fbdev: pxafb: match_string() conversion fixup

"unknown" lcd_types[] entry is needed for proper operation of
the driver, add it back.

Fixes: 6d09dfe70f8f ("video: fbdev: pxafb: Convert to use match_string() helper")
Reported-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

drivers/video/fbdev/pxafb.c

@@ -2099,7 +2099,7 @@ static void pxafb_check_options(struct device *dev, struct pxafb_mach_info *inf)
 
 #if defined(CONFIG_OF)
 static const char * const lcd_types[] = {
-	"mono-stn", "mono-dstn", "color-stn", "color-dstn",
+	"unknown", "mono-stn", "mono-dstn", "color-stn", "color-dstn",
 	"color-tft", "smart-panel", NULL
 };