dt-bindings: display: Add support for Intel KeemBay Display

This patch adds bindings for Intel KeemBay Display

v2: review changes from Rob Herring
v3: review changes from Sam Ravnborg (removed mipi dsi entries, and
    encoder entry, connect port to dsi)
    MSSCAM is part of the display submodule and its used to reset LCD
    and MIPI DSI clocks, so its best to be on this device tree.
v4: review changes from Neil Armstrong and Sam - removed msscam
    entries

Signed-off-by: Anitha Chrisanthus <anitha.chrisanthus@intel.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Rob Herring <robh@kernel.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1604538931-26726-2-git-send-email-anitha.chrisanthus@intel.com