video: fbdev: au1200fb: Fix a potential double free

If 'fb_alloc_cmap()' fails, 'fbi->pseudo_palette' is freed and an error
code is returned by 'au1200fb_init_fbinfo()'.
The only caller, 'au1200fb_drv_probe()' goes to an error handling path
where resources allocated in 'fb_alloc_cmap()' are freed.
This leads to a double free of 'fbi->pseudo_palette'.

Fix it by letting the caller free all resources in case of failure in
'au1200fb_init_fbinfo()'.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>