This patch gets rid of the tcp_default_win_scale sysctl and instead
computes the optimum maximum window scale.  It just means one less
thing to have to tune.  I also moved the code out of the inline because
it gets called three places and isn't in the critical path.

As a side effect, it will cause a smaller window scale for many people
since the default tcp_rmem fits in a win_scale of 2.  This is allows for
finer grain windows (good), but may mask some of the problems with bad
implementations we have already seen (bad).
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@redhat.com>