ubifs: Pass folios to acomp

As the acomp interface supports folios, use that instead of mapping
the data in ubifs.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Zhihao Cheng <chengzhihao1@huawei.com> # For xfstests
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>