selftests/powerpc: Fix core-pkey for default execute permission change

Only when the key is allocated, its permission are enabled.
Reviewed-by: NThiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: NRam Pai <linuxram@us.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

tools/testing/selftests/powerpc/ptrace/core-pkey.c

@@ -140,6 +140,10 @@ static int child(struct shared_info *info)
 
 	if (disable_execute)
 		info->iamr |= 1ul << pkeyshift(pkey1);
+	else
+		info->iamr &= ~(1ul << pkeyshift(pkey1));
+
+	info->iamr &= ~(1ul << pkeyshift(pkey2) | 1ul << pkeyshift(pkey3));
 
 	info->uamor |= 3ul << pkeyshift(pkey1) | 3ul << pkeyshift(pkey2);