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

module/icp/io/aes.c

@@ -35,6 +35,7 @@
 #include <sys/modctl.h>
 #define	_AES_IMPL
 #include <aes/aes_impl.h>
+#include <modes/gcm_impl.h>
 
 #define	CRYPTO_PROVIDER_NAME "aes"
 
@@ -205,6 +206,10 @@ aes_mod_init(void)
 {
 	int ret;
 
+	/* find fastest implementations and set any requested implementations */
+	aes_impl_init();
+	gcm_impl_init();
+
 	if ((ret = mod_install(&modlinkage)) != 0)
 		return (ret);