fix(rockchip-rk3588): Enable mesa-vpu extension for GPU acceleration

The mesa-vpu extension author stated this 'should be enabled on all
for rk3588 distributions' but was never implemented. Without it,
desktop images use llvmpipe software rendering instead of GPU.

The extension has built-in logic to only apply where appropriate
(vendor kernel, desktop builds, supported releases).

Tested on Orange Pi 5 Plus: glxinfo now shows Mali-G610 (Panfrost).

Closes: #7507, #7504

Author: brainwavecoder9

config/sources/families/rockchip-rk3588.conf

@@ -13,6 +13,7 @@ BOOTSOURCE='https://github.com/radxa/u-boot.git'
 BOOTBRANCH='branch:next-dev-v2024.10' # Always use same version as rk35xx, they share a patch dir
 BOOTPATCHDIR="legacy/u-boot-radxa-rk35xx"
 OVERLAY_PREFIX='rockchip-rk3588'
+ENABLE_EXTENSIONS="mesa-vpu"
 
 case $BRANCH in