[AGPGART] Fix Nforce modular compilation.

I really don't like exporting this, but right now its the cleanest way.
It will go away at some point.

drivers/char/agp/generic.c

@@ -39,6 +39,9 @@
 
 __u32 *agp_gatt_table; 
 int agp_memory_reserved;
+/* Needed by the Nforce GART driver for the time being. Would be
+ * nice to do this some other way instead of needing this export. */
+EXPORT_SYMBOL_GPL(agp_memory_reserved);
 
 /* 
  * Generic routines for handling agp_memory structures -