Add a new buffer type created with LIMA_BO_FLAG_HEAP whose backup memory size is dynamically increased when GP report lack of heap memory. So we just need to create a big enough heap buffer which won't really cost that much memory until it really needs.
Kernel patch is under review here: https://patchwork.freedesktop.org/series/72110/
The bug which caused MMU fault has been fixed in kernel driver, and I've tested these changes with glmark2 and some desktop application, so ready to review now.