staging: comedi: daqboard2000: check result of FPGA programming

According to an old, GPL'ed Linux driver at
<ftp://ftp.mccdaq.com/downloads/iotech_software/DaqBoard_1000_2000_Series/Linux_driver_kernelv2.4.x/

>,
after programming the FPGA, the General Purpose Input (USERI) of the PLX
PCI-9080 should go high shortly after a valid FPGA bitstream has been
loaded.  Add a new function `daqboard2000_wait_fpga_programmed()` to
wait for that, performing up to 200 checks over a 20 ms period (this is
loosely based on `pollFPGADone()` in the above-mentioned old driver).
Return 0 if the FPGA appears to have loaded successfully, or
`-ETIMEDOUT` if it runs out of checks.  Call it from the firmware
loading callback `daqboard2000_load_firmware()` after writing the
firmware to the FPGA to check it is programmed successfully.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>