fbdev: sm501fb: Fix buffer errors in OF binding code

fbdev: sm501fb: Fix buffer errors in OF binding code

The code that gets the frame buffer mode from OF has 'use after free',
'buffer overrun' and memory leaks.

info->edid_data isn't free if the probe functions fail or if
pd->def_mode is set.

If both the CRT and PANEL are enabled info->edid_data is used after
being freed and is freed twice.

The string returned by of_get_property(np, "mode", &len) is just
written over either the static "640x480-16@60" or the module parameter
string without any regard for the length (which is most likely longer).

Use kstrump() for the OF mode and free everything before freeing 'info.

Fixes: 4295f9bf74a88 ("video, sm501: add OF binding to support SM501")
Signed-off-by: David Laight <david.laight.linux@gmail.com>
Signed-off-by: Helge Deller <deller@gmx.de>