Add dma_streamer_mod for SDRDC DMA stack

Also clarified license language in spi_shim module
Add user-apps tree with lrzsz
Add DSA source under Apache 2.0 license
Tweaks to SDRDC build scripts

- Revised where SDRDC-specific output filenames are set, so in-tree petalinux builds stay
  consistent with full rebuilds
- Revised how vendors tree gets copied into petalinux tree so it happens more reliably
- Enable AD9361s in device-tree and synchronize their SPI mode
- Quiet some spurious error messages