dt-bindings: panel-simple: Add compatible for Frida FRD350H54004 LCD

Add bindings documentation for the Frida 3.5" (320x240 pixels) 24-bit
TFT LCD panel.

v2: Switch documentation from plain text to YAML
v3: Simply add new compatible to panel-simple.yaml file instead of
    adding new file

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200113161741.32061-2-paul@crapouillou.net