ipv6: remove sysctl jiffies conversion on gc_elasticity and min_adv_mss

sysctl output ipv6 gc_elasticity and min_adv_mss as values divided by
HZ. However, they are not in unit of jiffies, since ip6_rt_min_advmss
refers to packet size and ip6_rt_fc_elasticity is used as scaler as in
expire>>ip6_rt_gc_elasticity, so replace the jiffies conversion
handler will regular handler for them.

This has impact on scripts that are currently working assuming the
divide by HZ, will yield different results with this patch in place.

Signed-off-by: Min Zhang <mzhang@mvista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>