For re(4) controllers that uses new jumbo frame scheme(RTL8168C/D/E),

For re(4) controllers that uses new jumbo frame scheme(RTL8168C/D/E),
limit maximum RX buffer size to RE_RX_DESC_BUFLEN instead of
blindly configuring it to 16KB. Due to lack of documentation, re(4)
didn't allow jumbo frame on these controllers. However it seems
controller is confused with jumbo frame such that it can DMA the
received frame to wrong address instead of splitting it into
multiple RX buffers. Of course, this caused panic.

Since re(4) does not support jumbo frames on these controllers,
make controller drop frame that is longer than RE_RX_DESC_BUFLEN
sized frame. Fortunately RTL810x controllers, which do not support
jumbo frame, have no such issues but this change also limited
maximum RX buffer size allowed to RTL810x controllers. Allowing
16KB RX buffer for controllers that have no such capability is
meaningless.

MFC after:	3 days