AArch64: Enable fast shifts on Neoverse V1/N2

Enable the fast shift feature in Neoverse V1 and N2 tunings as well.

2021-10-20  Wilco Dijkstra  <wdijkstr@arm.com>

gcc/
	* config/aarch64/aarch64.c (neoversev1_tunings):
	Enable AARCH64_EXTRA_TUNE_CHEAP_SHIFT_EXTEND.
	(neoversen2_tunings): Likewise.

gcc/config/aarch64/aarch64.c

@@ -1839,7 +1839,8 @@ static const struct tune_params neoversev1_tunings =
   tune_params::AUTOPREFETCHER_WEAK,	/* autoprefetcher_model.  */
   (AARCH64_EXTRA_TUNE_CSE_SVE_VL_CONSTANTS
    | AARCH64_EXTRA_TUNE_USE_NEW_VECTOR_COSTS
-   | AARCH64_EXTRA_TUNE_MATCHED_VECTOR_THROUGHPUT),	/* tune_flags.  */
+   | AARCH64_EXTRA_TUNE_MATCHED_VECTOR_THROUGHPUT
+   | AARCH64_EXTRA_TUNE_CHEAP_SHIFT_EXTEND),	/* tune_flags.  */
   &generic_prefetch_tune
 };
@@ -1995,7 +1996,7 @@ static const struct tune_params neoversen2_tunings =
   2,	/* min_div_recip_mul_df.  */
   0,	/* max_case_values.  */
   tune_params::AUTOPREFETCHER_WEAK,	/* autoprefetcher_model.  */
-  (AARCH64_EXTRA_TUNE_NONE),	/* tune_flags.  */
+  (AARCH64_EXTRA_TUNE_CHEAP_SHIFT_EXTEND),	/* tune_flags.  */
   &generic_prefetch_tune
 };