Use CONFIG_EDID to make edid-generate.c and edid-region.c
configurable.

Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20190123065618.3520-26-yang.zhong@intel.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>