x86: Use generic TIF bits

No point in defining generic items and the upcoming RSEQ optimizations are
only available with this _and_ the generic entry infrastructure, which is
already used by x86. So no further action required here.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>