ARAM_SHIFT) and 64 bit arithmetic
is no longer necessary, simplifying the code.

Some example test measurements with the patched code (confirming no functional
change in the congestion avoidance algorithm) can be seen at:

http://www.hamilton.ie/doug/vegaspatch/

Signed-off-by: Doug Leith <doug.leith@nuim.ie>
Signed-off-by: David S. Miller <davem@davemloft.net>
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