<msm8916+secure boot-venus>: use separate firmware packages (MR 2619)

Rule D: Devices with secure boot and venus present in the firmware
        partition need:

  1. GPU firmware (firmware-qcom-adreno-a300)
  2. msm-firmware-loader (for wcnss, modem, venus)
  4. device-specific -wcnss-nv firmware

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