hw/pci/pci_host: Trace config accesses on unexisting functions

hw/pci/pci_host: Trace config accesses on unexisting functions

Currently we only emit trace events for existing PCI functions.
In order to ease debugging PCI enumeration process, also emit
for unexisting functions:

  $ qemu-system-foo -trace pci_cfg_\*
  ...
  pci_cfg_read empty 00:0a.4 @0x0 -> 0xffffffff
  pci_cfg_read empty 00:0a.5 @0x0 -> 0xffffffff
  pci_cfg_read empty 00:0a.6 @0x0 -> 0xffffffff
  pci_cfg_read empty 00:0a.7 @0x0 -> 0xffffffff
  pci_cfg_read pcnet 00:0b.0 @0x0 -> 0x20001022
  pci_cfg_read empty 00:0c.0 @0x0 -> 0xffffffff
  pci_cfg_read empty 00:0d.0 @0x0 -> 0xffffffff
  pci_cfg_read empty 00:0e.0 @0x0 -> 0xffffffff
  pci_cfg_read empty 00:0f.0 @0x0 -> 0xffffffff
  pci_cfg_read empty 00:10.0 @0x0 -> 0xffffffff
  pci_cfg_read empty 00:11.0 @0x0 -> 0xffffffff
  pci_cfg_read cirrus-vga 00:12.0 @0x0 -> 0xb81013

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230104133935.4639-2-philmd@linaro.org>