bnxt_en: add a dummy definition for bnxt_vf_rep_get_fid()

bnxt_en: add a dummy definition for bnxt_vf_rep_get_fid()

When bnxt VF-reps are not compiled in (CONFIG_BNXT_SRIOV is off)
bnxt_tc.c needs a dummy definition of the routine bnxt_vf_rep_get_fid().

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Fixes: 0474545ad12f ("bnxt_en: bnxt: add TC flower filter offload support")
Signed-off-by: Sathya Perla <sathya.perla@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>