stackdepot: respect __GFP_NOLOCKDEP allocation flag

commit 6fe60465 upstream.

If stack_depot_save_flags() allocates memory it always drops
__GFP_NOLOCKDEP flag.  So when KASAN tries to track __GFP_NOLOCKDEP
allocation we may end up with lockdep splat like bellow:

======================================================
 WARNING: possible circular locking dependency detected
 6.9.0-rc3+ #49 Not tainted
 ------------------------------------------------------
 kswapd0/149 is trying to acquire lock:
 ffff88811346a920
(&xfs_nondir_ilock_class){++++}-{4:4}, at: xfs_reclaim_inode+0x3ac/0x590
[xfs]

 but task is already holding lock:
 ffffffff8bb33100 (fs_reclaim){+.+.}-{0:0}, at:
balance_pgdat+0x5d9/0xad0

 which lock already depends on the new lock.

 the existing dependency chain (in reverse order) is:
 -> #1 (fs_reclaim){+.+.}-{0:0}:
        __lock_acquire+0x7da/0x1030
        lock_acquire+0x15d/0x400
        fs_reclaim_acquire+0xb5/0x100
 prepare_alloc_pages.constprop.0+0xc5/0...