staging: comedi: addi_eeprom: make the eeprom helper functions static

The functions used to read the eeprom header information blocks are
only used in this file. Move them to remove the need for the forward
declarations.

The i_EepromReadTimerHeader() function is currently not being used.
Block it out with and #if 0/#endif until it's determined if it should
be removed.
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>