dm: allow setting driver_data before/during bind

This will allow a driver's bind function to use the driver data. One
example is the Tegra186 GPIO driver, which instantiates child devices
for each of its GPIO ports, yet supports two different HW instances each
with a different set of ports, and identified by the udevice_id .data
field.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>