toolchain/gdb: 6.4 shouldn't be selectable for avr32

toolchain/gdb/Config.in

@@ -37,7 +37,7 @@ choice
 
 	config BR2_GDB_VERSION_6_4
 		bool "gdb 6.4"
-		depends on !BR2_nios2
+		depends on !BR2_avr32 && !BR2_nios2
 		depends on BR2_DEPRECATED
 
 	config BR2_GDB_VERSION_6_5