enic: detect SR-IOV VF type from PCI capability

enic: detect SR-IOV VF type from PCI capability

Read the VF device ID from the SR-IOV PCI capability at probe time to
determine whether the PF is configured for V1, USNIC, or V2 virtual
functions. Store the result in enic->vf_type for use by subsequent
SR-IOV operations.

The VF type is a firmware-configured property (set via UCSM, CIMC,
Intersight etc) that is immutable from the driver's perspective. Only
PFs are probed for this capability; VFs and dynamic vnics skip
detection.

Signed-off-by: Satish Kharat <satishkh@cisco.com>
Link: https://patch.msgid.link/20260401-enic-sriov-v2-prep-v4-3-d5834b2ef1b9@cisco.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>