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/asm-x86_64/modes/gcm_pclmulqdq.S

@@ -81,7 +81,7 @@
  */
 
 
-#if defined(lint) || defined(__lint)
+#if defined(lint) || defined(__lint)	/* lint */
 
 #include <sys/types.h>
 
@@ -90,7 +90,7 @@ void
 gcm_mul_pclmulqdq(uint64_t *x_in, uint64_t *y, uint64_t *res) {
 }
 
-#else	/* lint */
+#elif defined(HAVE_PCLMULQDQ)	/* guard by instruction set */
 
 #define _ASM
 #include <sys/asm_linkage.h>