odp-util: Fix parsing of Ethertypes 0x8000 and above.

odp-util: Fix parsing of Ethertypes 0x8000 and above.

An existing comment in the function being updated explains the problem:

    * Many of the sscanf calls in this function use oversized destination
    * fields because some sscanf() implementations truncate the range of %i
    * directives, so that e.g. "%"SCNi16 interprets input of "0xfedc" as a
    * value of 0x7fff.  The other alternatives are to allow only a single
    * radix (e.g. decimal or hexadecimal) or to write more sophisticated
    * parsers.