net/ice: enlarge Rx queue rearm threshold to 64

net/ice: enlarge Rx queue rearm threshold to 64

We observe performance drop on ice AVX512 data path after stop and
start by using testpmd.

As CPU polling is faster in AVX512 path, L3 contested accesses is
intensified when rxrearm_start is a random value after testpmd
stop/start.

Enlarge ICE_RXQ_REARM_THRESH to 64 to ease the contested accesses and
fix the performance drop issue.

Cc: stable@dpdk.org
Signed-off-by: Leyi Rong <leyi.rong@intel.com>
Acked-by: Qi Zhang <qi.z.zhang@intel.com>