arm64: dts: qcom: sdm845-oneplus: Describe Wi-Fi/BT properly

arm64: dts: qcom: sdm845-oneplus: Describe Wi-Fi/BT properly

The onboard Wi-Fi / BT device, WCN3990, has a simple on-chip PMU, which
further spreads generated voltage. Describe the PMU in the device tree
and rewire Bluetooth and WiFi supply properties to use the PMU LDO
outputs instead of referencing the SoC regulators directly.

Verified against the datasheet.

Assisted-by: Claude:claude-opus-4.6
Signed-off-by: David Heidelberg <david@ixit.cz>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20260327-wcn3990-pwrctl-sdm845-v1-2-3f5c34e3fdd0@ixit.cz
Signed-off-by: Bjorn Andersson <andersson@kernel.org>