arm64: dts: imx8mq-librem5-r3: Mark buck3 as always on

Commit 99e71c02 ("arm64: dts: imx8mq-librem5: Don't mark buck3 as always on")
removed always-on marking from GPU regulator, which is great for power
saving - however it introduces additional i2c0 traffic which can be deadly
for devices from the Dogwood batch.

To workaround the i2c0 shutdown issue on Dogwood, this commit marks
buck3 as always-on again - but only for Dogwood (r3).
Signed-off-by: NSebastian Krzyszkowiak <sebastian.krzyszkowiak@puri.sm>
Signed-off-by: NMartin Kepplinger <martin.kepplinger@puri.sm>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mq-librem5-r3.dts

@@ -28,6 +28,10 @@
 	ti,termination-current = <144000>;  /* uA */
 };
 
+&buck3_reg {
+	regulator-always-on;
+};
+
 &proximity {
 	proximity-near-level = <25>;
 };