Accton platforms: Correct the comments in onie-rom.conf

These platforms are including:
- AS4600_54T
- AS5600_52X
- AS5710_54X
- AS6700_32X
- AS6701_32X
- AS6710_32X

The onie-rom.conf were copid and revised from Accton 5652 (a.k.a.
AS5600_52x).  Some comments in thier onie-rom.conf were not quite
true.  We revise the sentances to conform to present fact.