atyfb: correct_chipset() can fail

Atari probe code relies on correct_chipset() failing if the device is not
a mach64 GX/CX.  aty_chips[] array would be indexed with -1 in that case.
Signed-off-by: NVille Syrjala <syrjala@sci.fi>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/video/aty/atyfb_base.c

@@ -424,7 +424,6 @@ static struct {
 #endif /* CONFIG_FB_ATY_CT */
 };
 
-/* can not fail */
 static int __devinit correct_chipset(struct atyfb_par *par)
 {
 	u8 rev;
@@ -437,6 +436,9 @@ static int __devinit correct_chipset(struct atyfb_par *par)
 		if (par->pci_id == aty_chips[i].pci_id)
 			break;
 
+	if (i < 0)
+		return -ENODEV;
+
 	name = aty_chips[i].name;
 	par->pll_limits.pll_max = aty_chips[i].pll;
 	par->pll_limits.mclk = aty_chips[i].mclk;