bnxt_en: Check valid VNIC ID in bnxt_hwrm_vnic_set_tpa().

During initialization, if we encounter errors, there is a code path that
calls bnxt_hwrm_vnic_set_tpa() with invalid VNIC ID.  This may cause a
warning in firmware logs.

Fixes: c0c050c5 ("bnxt_en: New Broadcom ethernet driver.")
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>