driver core: remove dev_attrs from struct class

Now that all in-kernel users of the dev_attrs field are converted to use
dev_groups, we can safely remove dev_attrs from struct class.

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

diff --cc drivers/base/core.c
Simple merge

diff --cc include/linux/device.h
Simple merge