erofs: fix kvcalloc() misuse with __GFP_NOFAIL

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: [email protected]
Fixes: fe3e5914e6dc ("erofs: try to leave (de)compressed_pages on stack if possible")
Fixes: 4f05687fd703 ("erofs: introduce struct z_erofs_decompress_backend")
Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Gao Xiang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]