selftests: firmware: Fix the request_firmware_into_buf() test for XZ format

The test uses a different firmware name, and we forgot to adapt for
the XZ compressed file tests.

https://lore.kernel.org/all/20210127154939.13288-1-tiwai@suse.de/



Fixes: 17980459 ("selftests: firmware: Add request_firmware_into_buf tests")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20220421152908.4718-4-tiwai@suse.de


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>