staging: comedi: addi_eeprom: cleanup i_EepromReadDigitalOutputHeader()

Add namespace by renaming this CamelCase function to
addi_eeprom_read_do_info().

Refactor the function so that it stores the data from the eeprom directly
in the private data instead of using the a struct to pass the data back
to i_EepromReadMainHeader(). This allows removing the str_DigitalOutputHeader
struct.

The return value is always 0 and it's never checked. Change it to void.

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