crypto: atmel - Fix -Wunused-const-variable warning

drivers/crypto/atmel-i2c.h:68:3: warning:
 error_list defined but not used [-Wunused-const-variable=]

error_list is only used in atmel-i2c.c,
so just move the definition over there.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>