sched: Add some KABI padding

JIRA: https://issues.redhat.com/browse/RHEL-114238
Upstream Status: RHEL Only
Depends: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-10/-/merge_requests/1424

Add a bit of KABI padding to help potential z-stream
fixes.  We are doing a smaller collection than had
been done in the past due to the new KABI restrictions.
Only a handful have been used in RHEL9 so far. This
set hits some of the structures that seem most likely
to have potential changes due to active developement
(sched_ext, eevdf etc). Add a few more for task_struct.

Signed-off-by: Phil Auld <pauld@redhat.com>

Author: auldp

include/linux/sched.h

@@ -611,6 +611,9 @@ struct sched_entity {
 	 * collide with read-mostly values above.
 	 */
 	struct sched_avg		avg;
+
+	RH_KABI_RESERVE(1)
+	RH_KABI_RESERVE(2)
 };
 
 struct sched_rt_entity {
@@ -1637,6 +1640,11 @@ struct task_struct {
 	struct user_event_mm		*user_event_mm;
 #endif
 
+	RH_KABI_RESERVE(1)
+	RH_KABI_RESERVE(2)
+	RH_KABI_RESERVE(3)
+	RH_KABI_RESERVE(4)
+
 	/*
 	 * New fields for task_struct should be added above here, so that
 	 * they are included in the randomized portion of task_struct.

kernel/sched/sched.h

@@ -744,6 +744,7 @@ struct cfs_rq {
 	struct list_head	throttled_csd_list;
 #endif /* CONFIG_CFS_BANDWIDTH */
 #endif /* CONFIG_FAIR_GROUP_SCHED */
+	RH_KABI_RESERVE(1)
 };
 
 #ifdef CONFIG_SCHED_CLASS_EXT
@@ -784,6 +785,7 @@ struct scx_rq {
 	struct balance_callback	deferred_bal_cb;
 	struct irq_work		deferred_irq_work;
 	struct irq_work		kick_cpus_irq_work;
+	RH_KABI_RESERVE(1)
 };
 #endif /* CONFIG_SCHED_CLASS_EXT */
 
@@ -1012,6 +1014,8 @@ struct root_domain {
 	cpumask_var_t		rto_mask;
 	struct cpupri		cpupri;
 
+	RH_KABI_RESERVE(1)
+
 	/*
 	 * NULL-terminated list of performance domains intersecting with the
 	 * CPUs of the rd. Protected by RCU.
@@ -1288,6 +1292,8 @@ struct rq {
 	call_single_data_t	cfsb_csd;
 	struct list_head	cfsb_csd_list;
 #endif
+	RH_KABI_RESERVE(1)
+	RH_KABI_RESERVE(2)
 };
 
 #ifdef CONFIG_FAIR_GROUP_SCHED