selftests/powerpc: Add core file test for Protection Key registers

This test verifies that the AMR, IAMR and UAMOR are being written to a
process' core file.
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
[mpe: Simplify make rule]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

tools/testing/selftests/powerpc/ptrace/Makefile

 # SPDX-License-Identifier: GPL-2.0
 TEST_PROGS := ptrace-gpr ptrace-tm-gpr ptrace-tm-spd-gpr \
               ptrace-tar ptrace-tm-tar ptrace-tm-spd-tar ptrace-vsx ptrace-tm-vsx \
-              ptrace-tm-spd-vsx ptrace-tm-spr ptrace-hwbreak ptrace-pkey
+              ptrace-tm-spd-vsx ptrace-tm-spr ptrace-hwbreak ptrace-pkey core-pkey
 
 include ../../lib.mk
 
@@ -9,8 +9,8 @@ all: $(TEST_PROGS)
 
 CFLAGS += -m64 -I../../../../../usr/include -I../tm -mhtm -fno-pie
 
-ptrace-pkey: child.h
-ptrace-pkey: LDLIBS += -pthread
+ptrace-pkey core-pkey: child.h
+ptrace-pkey core-pkey: LDLIBS += -pthread
 
 $(TEST_PROGS): ../harness.c ../utils.c ../lib/reg.S ptrace.h