power: extend prefix match to regulator-name property

This patch extends pmic_bind_children prefix matching. In addition to
the node name the property regulator-name is used while trying to match
prefixes. This allows assigning different drivers to regulator nodes
named regulator@1 and regulator@10 for example.
I have discarded the idea of using other properties then regulator-name
as I do not see any benefit in using property compatible or even
regulator-compatible. Of course I am open to change this if there are
good reasons to do so.

Signed-off-by: Felix Brack <fb@ltec.ch>
Reviewed-by: Simon Glass <sjg@chromium.org>