dm: core: Widen the dump tree to show more of the driver's name.

With drivers that have prefix names that are quite long (like
'versatile_') it is useful to have a wider column for the driver's
name when dumping the device driver tree.

Also update the tests to take into account the wider output format.

Signed-off-by: Liviu Dudau <liviu.dudau@foss.arm.com>
Reviewed-by: Simon Glass <sjg@chromium.org>