[AGPGART] Fix up the reserved bits.

The previous checks were against AGP_STAT values, but userspace passes us
an agp command register.

drivers/char/agp/agp.h

@@ -315,7 +315,7 @@ extern int agp_try_unsupported_boot;
 #define AGPCTRL_APERENB		(1<<8)
 #define AGPCTRL_GTLBEN		(1<<7)
 
-#define AGP2_RESERVED_MASK 0x00fffdc8
-#define AGP3_RESERVED_MASK 0x00ff0180
+#define AGP2_RESERVED_MASK 0x00fffcc8
+#define AGP3_RESERVED_MASK 0x00ff00cc
 
 #endif	/* _AGP_BACKEND_PRIV_H */