x86/fpu: Use task_disable_lazy_fpu_restore() helper

Replace magic assignments of fpu.last_cpu = ~0 with more explicit
task_disable_lazy_fpu_restore() calls.

Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1423252925-14451-8-git-send-email-riel@redhat.com


Signed-off-by: Borislav Petkov <bp@suse.de>