board/qemu/riscv32-virt: convert Linux defconfig into a fragment

Convert the config to the arch defconfig plus a fragment. When this
fragment is applied we will generate the same config as we previously
did.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
3 files changed