x86/pti: Enable PTI by default

This really want's to be enabled by default. Users who know what they are
doing can disable it either in the config or on the kernel command line.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org

security/Kconfig

@@ -56,6 +56,7 @@ config SECURITY_NETWORK
 
 config PAGE_TABLE_ISOLATION
 	bool "Remove the kernel mapping in user mode"
+	default y
 	depends on X86_64 && !UML
 	help
 	  This feature reduces the number of hardware side channels by