driver-core: prepare for 2.6.27 api change by adding dev_set_name

Create the dev_set_name function now so that various subsystems can
start changing over to it before other changes in 2.6.27 will make it
compulsory.

Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>