Export linux-rt (PREEMPT_RT) specific symbols needed by ZFS.
(Regular kernel provides them static inline in linux/preempt.h.)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1812 +1812 @@ void migrate_disable(void)
-EXPORT_SYMBOL_GPL(migrate_disable);
+EXPORT_SYMBOL(migrate_disable);
@@ -1843 +1843 @@ void migrate_enable(void)
-EXPORT_SYMBOL_GPL(migrate_enable);
+EXPORT_SYMBOL(migrate_enable);