cli: Fixed bladerf_is_fpga_configured() calls to check for errors

Also removed an extranous check of state->curr_device and FPGA from
print_gpio, as this will be checked in cmd_print before print_gpio
is called.
hdl: Touched up hdl README.md to provide a few more details
Merge branch 'bladerf' of github.com:Nuand/bladeRF into dev-cli_add_rx_tx
linux_driver: Added patch from mainline that I failed to merge