net: increase max queues to 64

net: increase max queues to 64

max supported queues tx + rx = 256, so 128 for combined
https://lists.gnu.org/archive/html/qemu-devel/2015-03/msg03917.html

But from above link it also seems that x86 only supports 80 pairs in
practice, so for now "only" quadruple the limit to 64 and see if we
get user feedback for more requested.

Signed-off-by: Alexandre Derumier <aderumier@odiso.com>
 [ T: reduce from 128 to 64 and add short rationale for that ]
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>