Transceiver52M: Add multi channel transceiver support

This patch primarily addresses devices with multiple RF front end
support. Currently device support is limited to UmTRX.

Vectorize transceiver variables to allow multiple asynchronous
threads on the upper layer with single downlink and uplink threads
driving the UHD I/O interface synchronously.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
12 files changed