crypto: atmel-i2c - avoid defines prefixed with CONFIG

Defines prefixed with "CONFIG" should be limited to proper Kconfig options,
that are introduced in a Kconfig file.

Here, a definition for the driver's configuration zone is named
CONFIG_ZONE. Rename this local definition to CONFIGURATION_ZONE to avoid
defines prefixed with "CONFIG".

No functional change.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>