Update vect_char_add target selector to use its own cache

This patch updates the vect_char_add target selector to use its own
cache instead of the vect_int cache.

This was causing a situation where bb-slp-40.c would fail on sparc when
run after other tests that use the vect_int target selector, but pass
when run on its own.

2019-11-26  Joel Hutton  <Joel.Hutton@arm.com>

gcc/testsuite/
	PR testsuite/92391
	* lib/target-supports.exp (check_effective_target_vect_char_add):
	Use a separate cache entry from vect_int.

From-SVN: r278738

gcc/testsuite/ChangeLog

+2019-11-26  Joel Hutton  <Joel.Hutton@arm.com>
+
+	PR testsuite/92391
+	* lib/target-supports.exp (check_effective_target_vect_char_add):
+	Use a separate cache entry from vect_int.
+
 2019-11-26  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/92648

gcc/testsuite/lib/target-supports.exp

@@ -5753,7 +5753,7 @@ proc check_effective_target_vect_bswap { } {
 # one vector length.
 
 proc check_effective_target_vect_char_add { } {
-    return [check_cached_effective_target_indexed vect_int {
+    return [check_cached_effective_target_indexed vect_char_add {
       expr {
          [istarget i?86-*-*] || [istarget x86_64-*-*]
          || ([istarget powerpc*-*-*]