dm: treewide: Use uclass_first_device_err when accessing one device

dm: treewide: Use uclass_first_device_err when accessing one device

There is a number of users that use uclass_first_device to access the
first and (assumed) only device in uclass.

Some check the return value of uclass_first_device and also that a
device was returned which is exactly what uclass_first_device_err does.

Some are not checking that a device was returned and can potentially
crash if no device exists in the uclass. Finally there is one that
returns NULL on error either way.

Convert all of these to use uclass_first_device_err instead, the return
value will be removed from uclass_first_device in a later patch.

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
Reviewed-by: Simon Glass <sjg@chromium.org>