IB: nes: convert to use DRIVER_ATTR_RW

We are trying to get rid of DRIVER_ATTR(), and all of the nes.c driver
attributes can be trivially changed to use DRIVER_ATTR_RW(), making the
code smaller and easier to manage over time.

Cc: Faisal Latif <faisal.latif@intel.com>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Sean Hefty <sean.hefty@intel.com>
Cc: Hal Rosenstock <hal.rosenstock@gmail.com>
Cc: <linux-rdma@vger.kernel.org>
Reviewed-by: Bart Van Assche <Bart.VanAssche@sandisk.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>