net: ethernet: oa_tc6: Improve the error recovery

In the Linux kernel, the following vulnerability has been resolved:

net: ethernet: oa_tc6: Improve the error recovery

When oversubscribed traffic causes lot of buffer overflow errors,
probably due to loss of data chunks, driver fails to find a
data chunk with end_valid bit set, before it runs out of sk buffer
space. As a result, assert is seen during skb_put.

Now, check is made if skb buffer has enough tailroom for the
incoming data before accepting. If there is no room, current
frame is abandoned and it will start looking for a data chunk
with start_valid bit, that is a new frame.

SK buffer allocation error is considered as recoverable error.

rx_buf_overflow flag is too specific and no longer the only
condition this flag is used for. Therefore it is renamed as
wait_until_start_valid. This is more appropriate as this flag
is used to look for the next data chunk with SV bit set, after
failures like buffer overflow, buffer allocation failure, skb pointer
validity besides buffer overflow error.

Not writing to status0 if it reads 0.