kernel: service BAR0/BAR1 region reads and extended config-space writes

Two more retry loops surfaced once the guest driver got past the CE binding:

- BAR0 region reads returned -EINVAL ("would be handled by mmap"), so a
  QEMU-trapped read of BAR0+0x88084 failed and the driver polled it forever.
  Serve reads from the BAR0 shadow/trap handler (and mirror BAR1 reads from
  the emulated vidmem backing).
- Config-space writes above offset 0xFF were refused with -EINVAL, so the
  driver's write to extended config 0x704 (PCIe device control area) never
  took effect and it retried. Accept and store extended-space writes; keep
  the legacy identity registers fixed.

0 files changed, 0 insertions, 0 deletions