rs6000: Move more g++.dg powerpc tests to g++.target

Also adjust DejaGnu directives, as specifically requiring "powerpc*-*-*" is no
longer required.

2022-04-15  Paul A. Clarke  <pc@us.ibm.com>

gcc/testsuite
	* g++.dg/debug/dwarf2/const2.C: Move to g++.target/powerpc.
	* g++.dg/other/darwin-minversion-1.C: Likewise.
	* g++.dg/eh/ppc64-sighandle-cr.C: Likewise.
	* g++.dg/eh/simd-5.C: Likewise.
	* g++.dg/eh/simd-4.C: Move to g++.target/powerpc, adjust dg directives.
	* g++.dg/eh/uncaught3.C: Likewise.
	* g++.dg/other/spu2vmx-1.C: Likewise.

gcc/testsuite/g++.target/powerpc/simd-4.C

@@ -1,4 +1,4 @@
-/* { dg-do run { target powerpc*-*-darwin* } } */
+/* { dg-do run { target *-*-darwin* } } */
 /* { dg-options "-fexceptions -fnon-call-exceptions -O -maltivec" } */
 
 #include <cstdlib>

gcc/testsuite/g++.target/powerpc/spu2vmx-1.C

@@ -1,4 +1,4 @@
-/* { dg-do compile { target powerpc*-*-* } } */
+/* { dg-do compile } */
 /* { dg-require-effective-target powerpc_spu } */
 /* { dg-options "-maltivec" } */
 

gcc/testsuite/g++.target/powerpc/uncaught3.C

@@ -1,4 +1,4 @@
-// { dg-do compile { target powerpc*-*-darwin* } }
+// { dg-do compile { target *-*-darwin* } }
 // { dg-final { scan-assembler-not "__cxa_get_exception" } }
 // { dg-options "-mmacosx-version-min=10.4" }
 // { dg-additional-options "-Wno-deprecated" { target c++17 } }