arm64: dts: imx8mm-phycore-som: Assign regulator for dsi to lvds bridge

arm64: dts: imx8mm-phycore-som: Assign regulator for dsi to lvds bridge

Add a missing voltage regulator of 1.8v to the sn65dsi83
(dsi_lvds bridge) node. Due to the absence of this regulator, a fallback
dummy regulator is used and that triggers a warning message from the
kernel. Assigning the appropriate regulator avoids the warning.

Signed-off-by: Yashwanth Varakala <y.varakala@phytec.de>
Signed-off-by: Andrej Picej <andrej.picej@norik.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>