arm64: dts: qcom: Use recommended MBN firmware path

arm64: dts: qcom: Use recommended MBN firmware path

All Qualcomm firmwares uploaded to linux-firmware are in MBN format,
instead of split MDT.  Firmware for boards here is not yet in
linux-firmware, but if it gets accepted it will be MBN, not MDT.

Change might affect users of DTS which rely on manually placed firmware
files, not coming from linux-firmware package.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250108120530.156928-1-krzysztof.kozlowski@linaro.org
[bjorn: Updated subject]
Signed-off-by: Bjorn Andersson <andersson@kernel.org>