net: mvneta: Fix for_each_present_cpu usage

This patch convert the for_each_present in on_each_cpu, instead of
applying on the present cpus it will be applied only on the online cpus.
This fix a bug reported on
http://thread.gmane.org/gmane.linux.ports.arm.kernel/468173

.

Using the macro on_each_cpu (instead of a for_each_* loop) also ensures
that all the calls will be done all at once.

Fixes: f8642885 ("net: mvneta: Statically assign queues to CPUs")
Reported-by: Stefan Roese <stefan.roese@gmail.com>
Suggested-by: Jisheng Zhang <jszhang@marvell.com>
Suggested-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>