bnxt_en: Optimize bnxt_sriov_disable()

bnxt_en: Optimize bnxt_sriov_disable()

bnxt_sriov_disable() is invoked from 2 places:

1. When the user deletes the VFs.
2. During the unload of the PF driver instance.

Inside bnxt_sriov_disable(), driver invokes
bnxt_restore_pf_fw_resources() which in turn causes a close/open_nic().
There is no harm doing this in the unload path, although it is inefficient
and unnecessary.

Optimize the function to make it more efficient.

Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Pavan Chebbi <pavan.chebbi@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/20250917040839.1924698-4-michael.chan@broadcom.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>