staging: comedi: addi_eeprom: make v_EepromWaitBusy() static

This function is only used in this file. Move it to remove the need
for the forward declaration.

Also, remove the comment about an error in the data book. It's not
really an error just someones misunderstanding about doing a byte
read of a dword register.

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>