video: s3c-fb: correct window osd size offset values

Offset values for OSD size registers of window 1 and 2 are corrected.
The offset values of OSD size registers are as follows:
window0: VIDOSDC (0x8)
window1 and 2: VIDOSDD (0xc)
window3 and 4: not present

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>