hmi-controller: fix wrong background surface size

In current implementation, the size of the first application
layer is used for the background image of a display.

This is wrong because:
	1. The background surface should be fullscreen.
	2. Each display could have different resolution.

We should use the size of the base layer of each display
for the background image.

Signed-off-by: Emre Ucan <eucan@de.adit-jv.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
1 file changed