crypto: cavium - Fix couple of static checker errors

Fix the following smatch errors
cptvf_reqmanager.c:333 do_post_process() warn: variable dereferenced
before check 'cptvf'
cptvf_main.c:825 cptvf_remove() error: we previously assumed 'cptvf'
could be null

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: George Cherian <george.cherian@cavium.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>