pci: make critical

Without this even though ACME depends on PCI and
PCI is currently set up to fail, the ACME init routine
continues to be called:

Initializing x86 bare metal world
Number of init entries: 4
Initializing Memory ...
Completed initializing Memory !
Initializing PCI buses ...
Failed to initialize PCI buses on early init, but its not critical
Initializing ACME(TM) Driver ...
Completed initializing ACME(TM) Driver !
Early init for Kasan...
Booting bare metal
Calling start_kernel()...
Calling setup_arch work for Kasan...

By setting PCI to be critical we won't traverse on
to ACME's init as it depends on PCI. Technically in
the kernel we don't have things like this affect
boot init, this is just an example / demo of how an
init sequence can depend on another, and how to do
this.

Initializing x86 bare metal world
Number of init entries: 4
Initializing Memory ...
Completed initializing Memory !
Initializing PCI buses ...
Failed to initialize PCI buses on early init
Early init failed

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>