ASoC: Intel: soc-acpi-intel-rpl-match: add missing empty item

In the Linux kernel, the following vulnerability has been resolved:

ASoC: Intel: soc-acpi-intel-rpl-match: add missing empty item

There is no links_num in struct snd_soc_acpi_mach {}, and we test

!link->num_adr as a condition to end the loop in hda_sdw_machine_select().

So an empty item in struct snd_soc_acpi_link_adr array is required.