enic: reset fetch index

enic: reset fetch index

Since we are allowing rx ring size modification, reset fetch index
everytime. Otherwise it could have a stale value that can lead to a null
pointer dereference.

Signed-off-by: Govindarajulu Varadarajan <gvaradar@cisco.com>
Signed-off-by: Parvi Kaustubhi <pkaustub@cisco.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Orabug: 27587345
(cherry picked from commit e6cdfcc581866625980a89391be4e6a8b379d0c5)
Signed-off-by: Jack Vogel <jack.vogel@oracle.com>
Reviewed-by: Kirtikar Kashyap <kirtikar.kashyap@oracle.com>