m91: enable example AD9361 app by default
Use new library API for checking active channels
m90, m81: DSA check and control of ENSM state

- Check current ENSM mode and FDD enable for each enabled ADI part before DMA
- If ADI is in an active mode which supports user's DMA direction, proceed
- If ADI is configured for FDD but in sleep, wait, or alert, set mode to FDD, unless user
  has given -M switch to forbid mode switching, before starting DMA
- If user didn't give -M switch and we switched into FDD before starting DMA, switch to
  sleep mode after DMA