updated gdb support for nios2, thanks Atle

toolchain/gdb/Config.in

@@ -30,18 +30,19 @@ choice
 
 	config BR2_GDB_VERSION_6_2_1
 		bool "gdb 6.2.1"
-		depends on !BR2_avr32
+		depends on !BR2_avr32 && !BR2_nios2
 
 	config BR2_GDB_VERSION_6_3
 		bool "gdb 6.3"
-		depends on !BR2_avr32
+		depends on !BR2_avr32 && !BR2_nios2
 
 	config BR2_GDB_VERSION_6_4
 		bool "gdb 6.4"
+		depends on !BR2_nios2
 
 	config BR2_GDB_VERSION_6_5
 		bool "gdb 6.5"
-		depends on !BR2_avr32
+		depends on !BR2_avr32 && !BR2_nios2
 
 	config BR2_GDB_VERSION_6_6
 		bool "gdb 6.6"
@@ -49,7 +50,7 @@ choice
 
 	config BR2_GDB_VERSION_SNAPSHOT
 		bool "gdb snapshot"
-		depends on !BR2_avr32
+		depends on !BR2_avr32 && !BR2_nios2
 
 endchoice