crypto: qat - remove unused adf_devmgr_get_first

adf_devmgr_get_first has been unused since commit
4a4b0bad ("crypto: qat - fix crypto_get_instance_node function")

Remove it.

(Build tested only, I don't own the hardware)

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Acked-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>