Add support for selecting encryption backend

- Add two new module parameters to icp (icp_aes_impl, icp_gcm_impl)
  that control the crypto implementation.  At the moment there is a
  choice between generic and aesni (on platforms that support it).
- This enables support for AES-NI and PCLMULQDQ-NI on AMD Family
  15h (bulldozer) and newer CPUs (zen).
- Modify aes_key_t to track what implementation it was generated
  with as key schedules generated with various implementations
  are not necessarily interchangable.

Reviewed by: Gvozden Neskovic <neskovic@gmail.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tom Caputi <tcaputi@datto.com>
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Signed-off-by: Nathaniel R. Lewis <linux.robotdude@gmail.com>
Closes #7102 
Closes #7103

cmd/ztest/ztest.c

@@ -129,6 +129,7 @@
 #include <zfs_fletcher.h>
 #include <libnvpair.h>
 #include <libzfs.h>
+#include <sys/crypto/icp.h>
 #ifdef __GLIBC__
 #include <execinfo.h> /* for backtrace() */
 #endif
@@ -3836,6 +3837,13 @@ ztest_dataset_create(char *dsname)
 		VERIFY0(dsl_crypto_params_create_nvlist(DCP_CMD_NONE, props,
 		    crypto_args, &dcp));
 
+		/*
+		 * Cycle through all available encryption implementations
+		 * to verify interoperability.
+		 */
+		VERIFY0(gcm_impl_set("cycle"));
+		VERIFY0(aes_impl_set("cycle"));
+
 		fnvlist_free(crypto_args);
 		fnvlist_free(props);
 	}