ARM: dts: sun8i: r40: bananapi-m2-ultra: Fix WiFi regulator definitions

The design of the Bananapi M2 Ultra has both DLDO1 and DLDO2 regulators
provide power to the WiFi+BT module, which is based on the Broadcom
BCM43438 or BCM43430 chip. Each regulator output from the PMIC can supply
up to 200 mA. The datasheet of the chip suggests a maximum power draw of
up to 360 mA when transmitting, thus requiring two outputs from the PMIC
to handle the load. However the device tree only references one of them,
leaving the other unused and possibly turned off.

This patch marks both as always-on, since we don't have a proper binding
to specify two regulators as "bound together". The name and constraints
of DLDO2 are also added.

Fixes: da7ac948 ("ARM: dts: sun8i: Add board dts file for Banana Pi M2
		      Ultra")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>