Partially revert r199035.

Partially revert r199035.
Revision 1.158 says only lower ten bits of
BGE_RXLP_LOCSTAT_IFIN_DROPS register is valid. For BCM5761 case it
seems the controller maintains 16bits value for the register.
However 16bits are still too small to count all dropped packets
happened in a second. To get a correct counter we have to read the
register in bge_rxeof() which would be too expensive.

Pointed out by:	bde