A64-OLinuXino family boards (maybe others too) uses PG for USB vbus
enable/disable. However PG is supplied by DLDO4, which is not present
in the list of known regulators. This patch adds DLD04 to it.

Signed-off-by: Stefan Mavrodiev <stefan@olimex.com>
Change-Id: I31d3bb3e0004ccf5b282d08b530ee44979da0466