240519-01 - experimental debian sid image for the starfive visionfive2 riscv64 sbc

• this is just an experimental testing image, actually an updated version of the one from last year which is now using the regular debian sid repos as riscv64 is finally included there now
• see: https://github.com/hexdump0815/imagebuilder/tree/main/systems/starfive_visionfive2
• based on the debian sid/unstable riscv64 port
• the v5.15 kernel used is based on VF2_v2.10.4 of the starfive visionfive2 kernel tree and some patches from the icenowy star64 kernel tree - it is still the old kernel from last year as it works fine and if one wants to play around with special features building an own kernel will be required anyway
• framebuffer console added (part of the patches mentioned above)
• a v5.15 backport of mglru added (multigen lru mm patches, which were merged into v6.1 mainline and improve performance especially in low memory situations)
• no gpu support as i'll not touch this until a proper open source driver is available - the legacy img stuff is just a waste of time to play around with ...
• has some features typical for the images here: btrfs rootfs with zstd compression, zswap with zstd compression, mgrlu enabled by default
• please switch the dip switches on the board to "sd", i.e. upper one (marked rgpio_1) to 0 (marked ON on the dip switch, i.e. default setting) and lower one (marked rgpio_0) to 1 (marked 2 on the dip switch, i.e. oposite to the default setting) to boot directly from the sd card as this image has sbi/u-boot included in its boot blocks (taken from the 202302 starfive debian image)
• username/password is as usual linux/changeme
• in case an image should not properly boot on your system, then please add a comment here: #130
• in case everything is working well, feel free to leave a comment here: #141