video: fbdev: neofb: fix memory leak in neo_scan_monitor()

neofb_probe() calls neo_scan_monitor() that can successfully allocate a
memory for info->monspecs.modedb and proceed to case 0x03. There it does
not free the memory and returns -1. neofb_probe() goes to label
err_scan_monitor, thus, it does not free this memory through calling
fb_destroy_modedb() as well. We can not go to label err_init_hw since
neo_scan_monitor() can fail during memory allocation. So, the patch frees
the memory directly for case 0x03.

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Evgeny Novikov <novikov@ispras.ru>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200630195451.18675-1-novikov@ispras.ru

drivers/video/fbdev/neofb.c

@@ -1819,6 +1819,7 @@ static int neo_scan_monitor(struct fb_info *info)
 #else
 		printk(KERN_ERR
 		       "neofb: Only 640x480, 800x600/480 and 1024x768 panels are currently supported\n");
+		kfree(info->monspecs.modedb);
 		return -1;
 #endif
 	default: