s390: support KPROBES_ON_FTRACE

Instead of using our own kprobes-on-ftrace handling convert the
code to support KPROBES_ON_FTRACE.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 287714d..cd84125 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -156,6 +156,7 @@
 	select HAVE_KERNEL_UNCOMPRESSED
 	select HAVE_KERNEL_XZ
 	select HAVE_KPROBES
+	select HAVE_KPROBES_ON_FTRACE
 	select HAVE_KRETPROBES
 	select HAVE_KVM
 	select HAVE_LIVEPATCH