dm: core: Add a way to set a device name

Some devices are bound entirely by probing and do not have the benefit of
a device tree to give them a name. This is very common with PCI and USB. In
most cases this is fine, but we should add an official way to set a device
name. This should be called in the device's bind() method.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>