crypto: caam - drop unexpected word 'a' in comments

Drop the unexpected word 'a' in the comments that need to be dropped

* This is a a cache of buffers, from which the users of CAAM QI driver
-->
* This is a cache of buffers, from which the users of CAAM QI driver

Signed-off-by: Jiang Jian <jiangjian@cdjrlc.com>
Reviewed-by: Gaurav Jain <gaurav.jain@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>