fx3_firmware: Cleaned up bladeRFAppThread_Entry

The loop in this function was rather strange, and theoretically
could roll over and reload the FPGA (albeit for an extreme uptime).
fx3_firmware: Added "device ready" query

This "device ready" status is used to denote that the device is
ready to be configured and used. Until the device becomes "ready"
all control requests will return an error.

This provides libbladeRF with a means to query when the device is done
loading an FPGA from flash, as well as any other firmware-based
initializations that may be needed in the future.
fx3_firmware: Version bump to v1.8.0

Minor rev incremented to denote added to "public" interface.
libbladeRF: Wait for device to report "ready" when opening it

This is intended to prevent the device from being opened while
firmware initializations (e.g., flash-based FPGA loading) complete.
fx3_firmware: Added sample .gdbinit file

Defaults for bladeRF FX3 debugging with the Segger J-Link