bcachefs: add missing sched_annotate_sleep()

bcachefs: add missing sched_annotate_sleep()

00594 ------------[ cut here ]------------
00594 do not call blocking ops when !TASK_RUNNING; state=2 set at [<000000003e51ef4a>] prepare_to_wait_event+0x5c/0x1c0
00594 WARNING: CPU: 12 PID: 1117 at kernel/sched/core.c:8741 __might_sleep+0x74/0x88
00594 Modules linked in:
00594 CPU: 12 UID: 0 PID: 1117 Comm: umount Not tainted 6.15.0-rc4-ktest-g3a72e369412d #21845 PREEMPT
00594 Hardware name: linux,dummy-virt (DT)
00594 pstate: 60001005 (nZCv daif -PAN -UAO -TCO -DIT +SSBS BTYPE=--)
00594 pc : __might_sleep+0x74/0x88
00594 lr : __might_sleep+0x74/0x88
00594 sp : ffffff80c8d67a90
00594 x29: ffffff80c8d67a90 x28: ffffff80f5903500 x27: 0000000000000000
00594 x26: 0000000000000000 x25: ffffff80cf5002a0 x24: ffffffc087dad000
00594 x23: ffffff80c8d67b40 x22: 0000000000000000 x21: 0000000000000000
00594 x20: 0000000000000242 x19: ffffffc080b92020 x18: 00000000ffffffff
00594 x17: 30303c5b20746120 x16: 74657320323d6574 x15: 617473203b474e49
00594 x14: 0000000000000001 x13: 00000000000c0000 x12: ffffff80facc0000
00594 x11: 0000000000000001 x10: 0000000000000001 x9 : ffffffc0800b0774
00594 x8 : c0000000fffbffff x7 : ffffffc087dac670 x6 : 00000000015fffa8
00594 x5 : ffffff80facbffa8 x4 : ffffff80fbd30b90 x3 : 0000000000000000
00594 x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffffff80f5903500
00594 Call trace:
00594  __might_sleep+0x74/0x88 (P)
00594  __mutex_lock+0x64/0x8d8
00594  mutex_lock_nested+0x28/0x38
00594  bch2_fs_ec_flush+0xf8/0x128
00594  __bch2_fs_read_only+0x54/0x1d8
00594  bch2_fs_read_only+0x3e0/0x438
00594  __bch2_fs_stop+0x5c/0x250
00594  bch2_put_super+0x18/0x28
00594  generic_shutdown_super+0x6c/0x140
00594  bch2_kill_sb+0x1c/0x38
00594  deactivate_locked_super+0x54/0xd0
00594  deactivate_super+0x70/0x90
00594  cleanup_mnt+0xec/0x188
00594  __cleanup_mnt+0x18/0x28
00594  task_work_run+0x90/0xd8
00594  do_notify_resume+0x138/0x148
00594  el0_svc+0x9c/0xa0
00594  el0t_64_sync_handler+0x104/0x130
00594  el0t_64_sync+0x154/0x158

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>