crypto: caam - Provide correct value to iounmap() in controller driver

Fix a "Trying to vfree() nonexistent vm area" error when unloading the CAAM
controller module by providing the correct pointer value to iounmap().

Signed-off-by: Victoria Milhoan <vicki.milhoan@freescale.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>