video: fbdev: au1200fb: Fix incorrect IRQ freeing

'au1200fb_drv_probe()' can not fail after a successful call to
'request_irq()'. So there is no point to call 'free_irq()' in the error
handling path.

Moreover, the hard coded AU1200_LCD_INT looks boggus since
commit 1630d85a ("au1200fb: fix hardcoded IRQ").

So, remove it.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: Tejun Heo <tj@kernel.org>
[b.zolnierkie: patch summary and description fixups]
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>