Add function of_alias_get_id() reporting -ENOSYS
for non-dt builds, so that drivers migrating to dt
can save some '#ifdef CONFIG_OF'.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com> Acked-by: Rob Herring <rob.herring@calxeda.com> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>