dm: Rename DM_GET_DEVICE() to DM_DRVINFO_GET()

This does not get a device (struct udevice *) but a struct driver_info *
so the name is confusing.

Rename it accordingly. Since we plan to have several various of these
macros, put GET at the end instead of the middle, so it is easier to spot
the related macros.

Signed-off-by: Simon Glass <sjg@chromium.org>