[BUGFIX] Add fieldname to ForeignMatchFields

This change adds the missing fieldname to the foreignMatchFields
based on the field's name. Without this the fieldname in the sys_file_references stays NULL and is difficult to actually use.

With this change added you can properly use it like this:

**Content Flexform**
```html
{namespace flux=Tx_Flux_ViewHelpers}
{namespace v=Tx_Vhs_ViewHelpers}
<f:layout name="Content" />

<f:section name="Configuration">
	<flux:flexform id="text-with-media" label="FAL Example">
		<flux:flexform.field.inline.fal name="someFiles" label="some Files" allowedExtensions='jpg,png' maxItems="8" />
	</flux:flexform>
</f:section>

<f:section name="Preview">
	<p>Elements: <f:count subject="{v:content.resources.fal(field:'someFiles')}" /></p>
</f:section>

<f:section name="Main">
	<f:for each="{v:content.resources.fal(field:'someFiles')}" as="file">
		{file.url}...
	</f:for>
</f:section>
```