Drivers can't be debugged with gdb. Here kgdb needs to be used, but AFAIK, most developers don't use a debugger with this stuff, but just log file output.
Of course you can use Eclipse to edit Kernel drivers and you can configurte Eclipse to compile them
AFAIK, technically, it is possible to use KGDB with a serial interface to debug Kernel drivers and configure eclipse to remote-control KGDB, but I am not aware of anybody doing this.
It might be possible to run the komplete system (Kernel and applications) with nios2-ide but I don't know if this makes much sense. Maybe someone who tried it might jump in here.
-Michael