device-huawei-alice: enable deviceinfo_create_initfs_extra and depend on postmarketos-base-downstream

Fix boot image being too big by adding deviceinfo_create_initfs_extra="true"

Add postmarketos-base-downstream to APKBUILD

Important notes: on branch edge, in the current state the device does not get past the splash screen but it does boot and can be interacted with trough SSH The system only boots, if it's installed on an SD Card.

formatting adjusted 2025-01-06 12:10 UTC, longnoserob