ubifs: Use crypto_acomp interface

Replace the legacy crypto compression interface with the new acomp
interface.

Remove the compression mutexes and the overallocation for memory
(the offender LZO has been fixed).

Cap the output buffer length for compression to eliminate the
post-compression check for UBIFS_MIN_COMPRESS_DIFF.

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