FMUv2: make all UARTs use 512 byte buffer, 2048 for CDCACM output

this is important when using UARTs for things like secondary GPS
modules, which may produce large enough transfers that 128 bytes is
not enough.

The 2048 buffer for CDCACM transmit makes mavlink log and parameter
transfer faster
FMUv2: enable RXDMA on 2nd GPS port and debug console

This should reduce the chance of lost data on these ports due to high
interrupt latency
meas_airspeed: avoid trivial dependency on math lib

including the math lib adds a huge amount to flash usage
FMUv1: use larger CDCACM buffer size for faster log transfer on FMUv1
ms5611: report P and T in ms5611 info
px4io: enable power on Spektrum connector on init