net/bnxt: fix VNIC allocation on port toggle

net/bnxt: fix VNIC allocation on port toggle

bnxt_init_chip called on port start keeps incrementing rx_cosq_cnt.
Hence more vnics are allocated with less number of rings on each port
stop/start operation. Eventually vnic allocation fails due to incorrect
ring group as no ring gets allocated to the vnic.

Fixes: 84d49664b5b2 ("net/bnxt: support CoS classification")
Signed-off-by: Santoshkumar Karanappa Rastapur <santosh.rastapur@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>