Commit 65c7923057 tried to clear the custom firmware path on exit by
writing a single space to the firmware_class.path parameter. This
doesn't work because nothing strips this space from the value stored
and fw_get_filesystem_firmware() only ignores zero-length paths.
Instead, write a null byte.
Fixes: 0a8adf5847 ("test: add firmware_class loader test")
Fixes: 65c7923057 ("test_firmware: fix setting old custom fw path back on exit")
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Acked-by: Luis R. Rodriguez <mcgrof@kernel.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>