LinuxSPIDeviceDriver: Bump bus to 16 bits

On Zynq, spidev enumerates the on-chip SPI buses as /dev/spidev32766,N etc,
so we need 16 bit to hold the bus number.

Signed-off-by: John Williams <john@whelanwilliams.net>
ZyboPilot: Add MS5611 on SPI CS 1

Signed-off-by: John Williams <john@whelanwilliams.net>
AP_HAL_Linux: Support for non-zero offset spidev busses

Some platforms don't enumerate /dev/spidevN.M from a zero bus offset.

Add support for this and use sprintf to allow for SPI buses > 9

Signed-off-by: John Williams <john@whelanwilliams.net>
Linux_SPI: Cleanup

Extend bus offset concept to GPIO chipselect mode

Remove debug message

White space format/cleanup

Signed-off-by: John Williams <john@whelanwilliams.net>
Zynq: Enable SPI-connected MPU9250 and MS5611

Signed-off-by: John Williams <john@whelanwilliams.net>