* make modules_initfs same as lg-hammerhead
(fixes postmarketOS splash logos at boot)
* split out downstream-firmware and mainline-firmware
* add firmware-adreno to firmware-mainline subpkg
* prepare deviceinfo file to mainline kernel
Prepare for better device categorization by moving everything to testing
subdir first.
[skip-ci]: chicken-egg problem: passing pmaports CI depends on pmbootstrap MR
depends on this MR
Related: postmarketos#16