zram: permit reclaim in zstd custom allocator

zram: permit reclaim in zstd custom allocator

When configured with pre-trained compression/decompression dictionary
support, zstd requires custom memory allocator, which it calls internally
from compression()/decompression() routines.  That means allocation from
atomic context (either under entry spin-lock, or per-CPU local-lock or
both).  Now, with non-atomic zram read()/write(), those limitations are
relaxed and we can allow direct and indirect reclaim.

Link: https://lkml.kernel.org/r/20250303022425.285971-17-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>