powerpc/ibmebus: Restore "name" sysfs attribute on ibmebus devices

Recent of_platform changes made of_bus_type_init() overwrite the bus
type's .dev_attrs list, meaning that the "name" attribute that ibmebus
devices previously had is no longer present.  This is a user-visible
regression which breaks the userspace eHCA support, since the eHCA
userspace driver relies on the name attribute to check for valid
adapters.

This fixes it by providing the "name" attribute in the generic OF
device code instead.  Tested on POWER.

Signed-off-by: Joachim Fenkes <fenkes@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>