crypto: bcm - Use the defined variable to clean code

Use the defined variable "dev" to make the code cleaner.

Signed-off-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Signed-off-by: Tang Bin <tangbin@cmss.chinamobile.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>