net/bnxt: fix error messages in VNIC prepare

net/bnxt: fix error messages in VNIC prepare

The bnxt_vnic_prep() can fail due to multiple reasons.
But when bnxt_vnic_prep() fails, PMD is not returning
the actual error/string to the application.

Fix it by moving the "rte_flow_error_set" to bnxt_vnic_prep()
to set the actual error code.

Fixes: d24610f7bfda ("net/bnxt: allow flow creation when RSS is enabled")
Cc: stable@dpdk.org
Signed-off-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Venkat Duvvuru <venkatkumar.duvvuru@broadcom.com>