devtool/standard.py: Create a copy of kernel source within work-shared if not present
If kernel source is not already downloaded i.e staging kernel dir is
empty, place a copy of the source when the user runs devtool modify
linux-yocto. This way the kernel source is available for other packages
that use it.
[YOCTO #10416]
Signed-off-by: Sai Hari Chandana Kalluri <chandana.kalluri@xilinx.com> Signed-off-by: Alejandro Enedino Hernandez Samaniego <alejandr@xilinx.com> Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
