arm64: dts: qcom: x1e80100-lenovo-yoga-slim7x: Enable IRIS

arm64: dts: qcom: x1e80100-lenovo-yoga-slim7x: Enable IRIS

IRIS firmware for the Lenovo Yoga Slim 7x is already upstream in
linux-firmware at qcom/x1e80100/LENOVO/83ED/qcvss8380.mbn, so enable IRIS
for the Slim 7x with the corresponding firmware-name property.

Tested-by: Anthony Ruhier <aruhier@mailbox.org>
Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Link: https://lore.kernel.org/r/20250915-x1e-iris-dt-v2-6-1f928de08fd4@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>