crypto: asymmetric_keys - fix uninitialized pointers with free attribute

crypto: asymmetric_keys - fix uninitialized pointers with free attribute

Uninitialized pointers with `__free` attribute can cause undefined
behavior as the memory assigned randomly to the pointer is freed
automatically when the pointer goes out of scope.

crypto/asymmetric_keys doesn't have any bugs related to this as of now,
but, it is better to initialize and assign pointers with `__free`
attribute in one statement to ensure proper scope-based cleanup

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/all/aPiG_F5EBQUjZqsl@stanley.mountain/
Signed-off-by: Ally Heev <allyheev@gmail.com>
Reviewed-by: Ignat Korchagin <ignat@cloudflare.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>