hw/i386/pc: Simplify DEFINE_I440FX_MACHINE() macro

hw/i386/pc: Simplify DEFINE_I440FX_MACHINE() macro

Last commit removed the last non-NULL use of DEFINE_I440FX_MACHINE
3rd parameter. 'compatfn' is now obsolete, remove it.

Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20240617071118.60464-22-philmd@linaro.org>