ARM: dts: qcom: rename WCNSS child name to bluetooth

The "bluetooth" is more popular and more descriptive than "bt", for a
Bluetooth device.  The WCNSS DT schema will expect such naming.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220405065752.27389-1-krzysztof.kozlowski@linaro.org