staging: comedi: cb_pcidas: fix cb_pcidas_eeprom_insn_read()

The comedi core expects (*insn_read) operations to return insn->n
data values. Refactor this function to work like the core expects.

For aesthetics, nvram_read() and use the comedi_timeout() helper
to handle the busy wait for the eeprom to be "ready".

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