PKGBUILD for Linux kernel 5.15 on StarFive VisionFive 2

Compatible for cross compile, run CARCH=riscv64 makepkg.
Kernel source code from https://github.com/starfive-tech/linux/
Config modified on top of https://gitlab.manjaro.org/packages/core/linux515/
CONFIG_USB_WIFI_ECR6600U turned off temporarily, please compile the driver yourself.