sched/x86_64: Don't save flags on context switch

sched/x86_64: Don't save flags on context switch

Now that the kernel always runs with clean flags (in particular,
NT is clear), there is no need to save and restore flags on
every context switch.

Signed-off-by: Andy Lutomirski <[email protected]>
Cc: Sebastian Lackner <[email protected]>
Cc: Anish Bhatt <[email protected]>
Cc: Chuck Ebbert <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Jan Beulich <[email protected]>
Link: http://lkml.kernel.org/r/bf6fb790787eb95b922157838f52712c25dda157.1412187233.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <[email protected]>