arm64: dts: msm8916-samsung-a5u: Override iris compatible

msm8916.dtsi sets the iris compatible to "qcom,wcn3620".
While WCN3620 seems to be used on most MSM8916 devices,
MSM8916 can also be paired with another chip (e.g. for WiFi dual-band).

A5U uses WCN3660B instead, so the compatible needs to be overridden
to apply the correct configuration.

However, simply using "qcom,wcn3660" would be incorrect,
since WCN3660B requires a slightly different regulator configuration
compared to WCN3660.

Instead, it requires the same configuration as "qcom,wcn3680".
Replace the compatible with "qcom,wcn3680" for A5U to make WCNSS
work correctly.

Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>