erofs: fix kvcalloc() misuse with __GFP_NOFAIL

As reported by syzbot [1], kvcalloc() cannot work with  __GFP_NOFAIL.
Let's use kcalloc() instead.

[1] https://lore.kernel.org/r/0000000000007796bd05f1852ec2@google.com

Reported-by:  <syzbot+c3729cda01706a04fb98@syzkaller.appspotmail.com>
Fixes: fe3e5914 ("erofs: try to leave (de)compressed_pages on stack if possible")
Fixes: 4f05687f

 ("erofs: introduce struct z_erofs_decompress_backend")
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20230110074927.41651-1-hsiangkao@linux.alibaba.com