Integrating more pre-git changes

- Add romfs-hacks to user-apps, for root filesystem tweaks when building
- Set USB mode to OTG and enable USB networking with RNDIS host
- Enable Dropbear SSH server
- Add an out/current symlink for most recent output files
Synchronize ad9361 tool with AFSE control branch

- Revised arguments for Set_ASFE_Mode command
- Add ADI_Get_AuxADCVoltage command
- Remove some debugging messages when using IIO driver
SPI bus numbering changes to support ASFE control

- Add bus-num support to spi_shim driver
- Add device-tree entry for spi-gpio for ASFE control with two spidev clients
- Set bus-num properties for rational numbering of SPI masters in SDRDC:
  - 0: QSPI
  - 1: spi-gpio for ASFE
  - 2: Zynq SPI for AD9361s
  - 3: spi_shim for AD1
  - 4: spi_shim for AD2