net: openvswitch: clean up some kernel-doc warnings

net: openvswitch: clean up some kernel-doc warnings

Fix some kernel-doc warnings in openvswitch.h:

Mark enum placeholders that are not used as "private" so that kernel-doc
comments are not needed for them.

Correct names for 2 enum values:
Warning: include/uapi/linux/openvswitch.h:300 Excess enum value
 '@OVS_VPORT_UPCALL_SUCCESS' description in 'ovs_vport_upcall_attr'
Warning: include/uapi/linux/openvswitch.h:300 Excess enum value
 '@OVS_VPORT_UPCALL_FAIL' description in 'ovs_vport_upcall_attr'

Convert one comment from "/**" kernel-doc to a plain C "/*" comment:
Warning: include/uapi/linux/openvswitch.h:638 This comment starts with
 '/**', but isn't a kernel-doc comment.
 * Omit attributes for notifications.

Add more kernel-doc:
- add kernel-doc for kernel-only enums;
- add missing kernel-doc for enum ovs_datapath_attr;
- add missing kernel-doc for enum ovs_flow_attr;
- add missing kernel-doc for enum ovs_sample_attr;
- add kernel-doc for enum ovs_check_pkt_len_attr;
- add kernel-doc for enum ovs_action_attr;
- add kernel-doc for enum ovs_action_push_eth;
- add kernel-doc for enum ovs_vport_attr;

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Ilya Maximets <i.maximets@ovn.org>
Link: https://patch.msgid.link/20260304012437.469151-1-rdunlap@infradead.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>