regulator: Add of_regulator_bulk_get_all()

regulator: Add of_regulator_bulk_get_all()

Merge series from Corentin Labbe <clabbe@baylibre.com>:

This adds a new regulator_bulk_get_all() which grab all supplies
properties in a DT node, for use in implementing generic handling
for things like MDIO PHYs where the physical standardisation of
the bus does not extend to power supplies.