The statistics histogram mode was not being explicitly initialized on
devices other than the 6390 family. Clearing the statistics then
overwrote the default setting, setting the histogram to a reserved
mode.

Explicitly set the histogram mode for all devices. Change the
statistics clear into a read/modify/write, and since it is now more
complex, move it into global1.c.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>