dt-bindings: drm/panel: simple: add lg,acx467akm-7 panel

Add binding for the LG ACX467AKM-7 4.95" 1080×1920 LCD panel that is
found on the LG Nexus 5 (hammerhead) phone. This appears to be a JDI
panel based on some Internet searches, however a specific model number
could not be found. I disassembled an old Nexus 5 with a broken
screen and the LG part number is the only model number present on the
back of the panel, so I think that is probably the best ID to use.
Signed-off-by: Brian Masney <masneyb@onstation.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20181124200628.24393-1-masneyb@onstation.org

Documentation/devicetree/bindings/display/panel/lg,acx467akm-7.txt

+LG ACX467AKM-7 4.95" 1080×1920 LCD Panel
+
+Required properties:
+- compatible: must be "lg,acx467akm-7"
+
+This binding is compatible with the simple-panel binding, which is specified
+in simple-panel.txt in this directory.