ltq-deu: fix cryptomgr test errors for des

When running cryptomgr tests against the driver, there are several
occurences of different errors for setkey of des and des3-ede
algorithms.
Those key checks are already implemented in the kernels des
implementation, so this is added as dependency and the kernel methods
are called. It also required adding the kernels des/des3 context
definitions to the des_ctx internal structure to be able to call the
kernel methods.
Fixed ifxdeu-des... setkey unexpectedly succeeded on test vector x;
expected_error=-22.
Fixed ifxdeu-des... setkey failed on test vector x; expected_error=0,
actual_error=-22.
Renamed des_ctx internal structure and des_encrypt/des_decrypt methods
because they are already defined in the kernel module.
Fixed wrong DES_xxx constant definitions in crypto_alg definition for
ifxdeu_des3_ede_alg.
Fixed method comment errors.

Signed-off-by: Daniel Kestrel <kestrel1974@t-online.de>