bnxt_en: Remove unused field "ref_count" in struct bnxt_ulp

bnxt_en: Remove unused field "ref_count" in struct bnxt_ulp

The "ref_count" field in struct bnxt_ulp is unused after
commit a43c26fa2e6c ("RDMA/bnxt_re: Remove the sriov config callback").
So we can just remove it now.

Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Signed-off-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Link: https://patch.msgid.link/20250417172448.1206107-4-michael.chan@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>