net: thunderx: Fix memory leak and other issues upon interface toggle

This patch fixes the following
1. When interface is being teardown and queues are being cleaned up,
   free pending SKBs that are in SQ which are either not transmitted
   or freed as NAPI is disabled by that time.
2. While interface initialization, delay CFG_DONE notification till
   the end to avoid corner cases where TXQs are enabled but CQ
   interrupts are not which results blocking transmission and kicking
   off watchdog.
3. Check for IFF_UP while re-enabling RBDR interrupts from tasklet.

Signed-off-by: Sunil Goutham <sgoutham@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>