sched: remove task_struct->faults_disabled_mapping

This reverts commit 2b69987 ("sched: Add
task_struct->faults_disabled_mapping"), which added this field without
review or maintainer signoff.  With bcachefs removed from the
tree it is also unused now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260122085223.487092-1-hch@lst.de

Author: Christoph Hellwig

include/linux/sched.h

@@ -955,7 +955,6 @@ struct task_struct {
 
 	struct mm_struct		*mm;
 	struct mm_struct		*active_mm;
-	struct address_space		*faults_disabled_mapping;
 
 	int				exit_state;
 	int				exit_code;

init/init_task.c

@@ -113,7 +113,6 @@ struct task_struct init_task __aligned(L1_CACHE_BYTES) = {
 	.nr_cpus_allowed= NR_CPUS,
 	.mm		= NULL,
 	.active_mm	= &init_mm,
-	.faults_disabled_mapping = NULL,
 	.restart_block	= {
 		.fn = do_no_restart_syscall,
 	},