ch-release-v6.12.8-20250613

build: Enable `CONFIG_FW_CFG_SYSFS_CMDLINE` as default configs

This enables integration test of the `fw_cfg` device [1].

[1] cloud-hypervisor/cloud-hypervisor#7117

Signed-off-by: Bo Chen <bchen@crusoe.ai>

github: Add riscv kernel build and upload

Add required pacakge for cross-compile riscv kernel, workflow for build
and upload kernel.

Signed-off-by: Ruoqing He <heruoqing@iscas.ac.cn>

build: Store default configurations in tree

Create a new `ch_defconfig` file and use that instead of downloading the
kernel from the CH repository.

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>

github: Add binary kernel binary build and upload

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>

Linux 5.4

Linux 5.4-rc8

Linux 5.4-rc7

Linux 5.4-rc6

Linux 5.4-rc5

Linux 5.4-rc4