linux-asos: Introduce linux-asos to manage our own kernel recipes

These will be similar to linux-yocto, but customized to the ASOS kernel
policies and support our reference HW.

qemuarm and qemuarm64 builds aren't yet supported by wic, but we can
still start building the kernels from a common base.

Signed-off-by: Amit Kucheria <amit.kucheria.ext@huawei.com>