arm64: dts: qcom: thinkpad-x13s: Fix firmware location

The firmware for the Lenovo Thinkpad X13s has been submitted, accepted
and merged upstream, so update to the correct path.

Signed-off-by: Steev Klimaszewski <steev@kali.org>
Reviewed-by: Andrew Halaney <ahalaney@redhat.com>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220817231236.3971-1-steev@kali.org