sysfs.h: remove attr_name() macro

Gotta love a macro that doesn't reduce the typing you have to do.

Also, only the driver core, and one network driver uses this.  The
driver core functions will be going away soon, and I'll convert the
network driver soon to not need this as well, so delete it for now
before anyone else gets some bright ideas and wants to use it.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>