ARM: dts: sun7i: olimex-lime2: Add regulators for GPIO banks

Make sure that A20 Olimex Lime2 pin bank regulators are
properly represented.

While pin banks A, B and F are connected to 3.3V static
regulator, pin banks E and G tied with LDO3 and LDO4 regulators
with 2.8V reference.

Signed-off-by: Priit Laes <priit.laes@paf.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>