staging: comedi: daqboard2000: replace daqboard2000_poll_cpld()

`daqboard2000_poll_cpld()` waits for a specified status bit in the CPLD
status register to be set, giving up after 50 tries over a period of
about 5 milliseconds.  It returns 1 if the status bit is set, otherwise
0.  It is only ever called to check the "INIT" status bit.  Replace it
with new function `daqboard2000_wait_cpld_init()`, which returns 0 if
the "INIT" status bit becomes set within 50 tries, or `-ETIMEDOUT` if
not set within 50 tries.  The firmware loading callback
`daqboard2000_load_firmware()` may return the error result from
`daqboard2000_wait_cpld_init()` if it has used up all its firmware
loading attempts and that was the last error.

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>