r8169: confusion between hardware and IP header alignment

The rx copybreak part is straightforward.

The align field in struct rtl_cfg_info is related to the alignment
requirements of the DMA operation. Its value is set at 2 to limit the
scale of possible regression but my old v1.21 8169 datasheet claims a
8 bytes requirements (which never appeared in the driver, of course)
and the 8101/8168 go with a plain 8 bytes alignment.

Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Cc: Edward Hsu <edward_hsu@realtek.com.tw>