drm_hwcomposer: Configuring Composer HAL to use sequential IDs

Implement Google guidelines from [1]

1. The supported display config IDs are:

    id=1, 1080x1920 60hz
    id=2, 1080x1920 50hz

2. When a change of display configs is processed, the next set of config IDs
   are assigned starting from the next unused integer, shown as follows:

    id=3, 2160x3840 60hz
    id=4, 2160x3840 50hz
    id=5, 1080x1920 60hz
    id=6, 1080x1920 50hz

+ Don't update modes in GetDisplayConfigs() . Modes is now updated at init or
after every hotplug event.

[1]: https://source.android.com/devices/graphics/hotplug#configuring-composer-hal-sequential-ids


Signed-off-by: Roman Stratiienko <roman.o.stratiienko@globallogic.com>