hw/pci: remove all references to find_i440fx function

hw/pci: remove all references to find_i440fx function

commit c0e427d6eb5fefc538 ("hw/acpi/ich9: Enable ACPI PCI hot-plug") removed all
uses of find_i440fx() function. This has been replaced by the more generic call
acpi_get_i386_pci_host() which maybe able to find the root bus both for i440fx
machine type as well as for the q35 machine type. There seems to be no more any
need to maintain a i440fx specific version of the api call. Remove it.

Tested by building from a clean tree successfully.

Signed-off-by: Ani Sinha <ani@anisinha.ca>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210825031949.919376-2-ani@anisinha.ca>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>