kvm tools: Do setup_fdt() later, get powerpc to boot again

kvm tools: Do setup_fdt() later, get powerpc to boot again

In commit e3d3ced "kernel load/firmware cleanup", the call to
kvm__arch_setup_firmware() was moved. Previously more or less at the end
of the init sequence, but that commit moved it into kvm__init() which
is a core_init() call and so runs quite early.

This broke booting powerpc guests, as setup_fdt() needs to be called
later in the setup sequence. In particular it looks at kvm->nrcpus,
which is uninitialised at that point.

In general setup_fdt() needs to run late in the sequence, as it encodes
the setup of the machine into the device tree.

So move setup_fdt() out of kvm__arch_setup_firmware() and make it a
firmware_init() call of its own.

With this patch I am able to boot guests again on HV KVM.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Pekka Enberg <penberg@kernel.org>