macsec: fix tracking of parent ifindex

For MACsec interfaces, kernel announces the parent ifindex in the
generic IFLA_LINK netlink attribute, which we save in
NMPlatformLink.parent. There is no need to have a dedicate member in
NMPlatformLnkMacsec.

The dedicate member was never set and during a restart of
NetworkManager the parent of the MACsec device could be unset leading
to a failed assertion:

  act_stage2_config: assertion 'parent' failed

Fixes: 85103656e9 ('platform: add support for macsec links')

https://bugzilla.redhat.com/show_bug.cgi?id=2122564
https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1481

src/core/devices/nm-device-macsec.c

@@ -153,8 +153,7 @@ update_properties(NMDevice *device)
 
     g_object_freeze_notify((GObject *) device);
 
-    if (priv->props.parent_ifindex != props->parent_ifindex)
-        nm_device_parent_set_ifindex(device, props->parent_ifindex);
+    nm_device_parent_set_ifindex(device, plink->parent);
 
 #define CHECK_PROPERTY_CHANGED(field, prop)      \
     G_STMT_START                                 \

src/libnm-platform/nm-platform.c

@@ -8044,7 +8044,6 @@ void
 nm_platform_lnk_macsec_hash_update(const NMPlatformLnkMacsec *obj, NMHashState *h)
 {
     nm_hash_update_vals(h,
-                        obj->parent_ifindex,
                         obj->sci,
                         obj->cipher_suite,
                         obj->window,
@@ -8064,7 +8063,6 @@ int
 nm_platform_lnk_macsec_cmp(const NMPlatformLnkMacsec *a, const NMPlatformLnkMacsec *b)
 {
     NM_CMP_SELF(a, b);
-    NM_CMP_FIELD(a, b, parent_ifindex);
     NM_CMP_FIELD(a, b, sci);
     NM_CMP_FIELD(a, b, icv_length);
     NM_CMP_FIELD(a, b, cipher_suite);

src/libnm-platform/nm-platform.h

@@ -814,7 +814,6 @@ typedef struct {
 } _nm_alignas(NMPlatformObject) NMPlatformLnkIpIp;
 
 typedef struct {
-    int     parent_ifindex;
     guint64 sci; /* host byte order */
     guint64 cipher_suite;
     guint32 window;