crypto: ccp - Fix DBC sample application error handling

The sample application was taking values from ioctl() and treating
those as the error codes to present to a user.

This is incorrect when ret is non-zero, the error is stored to `errno`.
Use this value instead.

Fixes: f40d42f1 ("crypto: ccp - Add a sample python script for Dynamic Boost Control")
Fixes: febe3ed3 ("crypto: ccp - Add a sample library for ioctl use")
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>