driver core: create write-only attribute macros for devices and drivers

This creates the macros DRIVER_ATTR_WO() and DEVICE_ATTR_WO() for
write-only attributes for drivers and devices.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Change-Id: I3ee718bcaa22536c4c54a3195ce2dc1160842d1d