arm64: dts: qcom: db410c: Fix Bluetooth LED trigger

Current LED trigger, 'bt', is not known/used by any existing driver.
Fix this by renaming it to 'bluetooth-power' trigger which is
controlled by the Bluetooth subsystem.

Fixes: 9943230c ("arm64: dts: qcom: Add apq8016-sbc board LED's related device nodes")
Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>