dt-bindings: Add Innolux P097PFG panel bindings

The Innolux P097PFG panel is 9.7" panel with 1536X2048
resolution, it reuse P079ZCA panel driver, so improve
p079ZCA dt-binding to support P097PFG.

Changes in v2:
- None
Changes in v3:
- None
Changes in v4:
- None
Changes in v5:
- use separate file for binding
- keep power supplies as required

Signed-off-by: Lin Huang <hl@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180702102721.3546-4-heiko@sntech.de