generic: add 8139cp fixes, enable hardware csum/tso on 4.0+

generic: add 8139cp fixes, enable hardware csum/tso on 4.0+

This contains two sets of fixes for the 8139cp driver.

For all kernel versions older than 4.3, we can apply the fixes from the
4.3-rc4 kernel. In particular, these fix the TX timeout recovery which
is causing my Geos to lock up until the hardware watchdog kicks in.

For 4.0 and later kernels, we can also apply the additional improvements
which are going into 4.4 to fix and enable hardware checksum/TSO
offload. Backporting those to older kernels is non-trivial.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@47220 3c298f89-4303-0410-b956-a3cf2f4a3e73