crypto: cavium - fix typos in comments

Replace 'is' with 'it'

file: drivers/crypto/cavium/cpt/cpt_hw_types.h
line: 268

*	which if the line hits and is is dirty will cause the line to be

changed to:
*	which if the line hits and it is dirty will cause the line to be

Signed-off-by: Jiang Jian <jiangjian@cdjrlc.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>