LU-13127 ptlrpc: don't require CONFIG_CRYPTO_CRC32

LU-13127 ptlrpc: don't require CONFIG_CRYPTO_CRC32

Don't require CONFIG_CRYPTO_CRC32 to build if not configured,
as it may not be available for all kernels and is easily fixed.

Consolidate the early reply code in sec_plain.c to also call
lustre_msg_calc_cksum() to reduce code duplication.

Fixes: e1a0f602a608 ("LU-13127 libcfs: make noise to console if CRC32 is missing")
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I00511df418ddfbd8522936cf2bc0f3193d2540e5
Reviewed-on: https://review.whamcloud.com/39201
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexey Lyashkov <alexey.lyashkov@hpe.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>