crypto: kpp - Add helper to set reqsize

mainline inclusion
from mainline-v6.2-rc1
commit 56861cbd
category: feature
bugzilla: https://gitee/com/openeuler/kernel/issues/16VW8E
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=56861cbde1b9f3b34d300e6ba87f2c3de1a9c309



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The value of reqsize should only be changed through a helper.
To do so we need to first add a helper for this.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: JangShui <yangjiangshui@h-partners.com>