linux-postmarketos-exynos5: upgrade to 6.1.56
Backported from our development branch:
- SPI flash for chromebooks;
- support for samsung-manta (see !4406 (merged) for status);
- fix performance of video decoder which drastically reduces lag when streaming games.
Tested on samsung-manta and google-snow. Could be tested on peach-pit and odroid-xu4, but it is mostly an upgrade to minor LTS version, so I don't think it is necessary