Revert "drm/i915/selftests: Convert timers to use timer_setup()"

This reverts commit 6d0dbd30

.

timer_setup_on_stack() does not yet exist:

In file included from drivers/gpu/drm/i915/i915_sw_fence.c:517:0:
drivers/gpu/drm/i915/selftests/lib_sw_fence.c: In function ‘timed_fence_init’:
drivers/gpu/drm/i915/selftests/lib_sw_fence.c:63:2: error: implicit declaration of function ‘timer_setup_on_stack’; did you mean ‘hrtimer_init_on_stack’? [-Werror=implicit-function-declaration]
  timer_setup_on_stack(&tf->timer, timed_fence_wake, 0);

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171025131336.2584-1-chris@chris-wilson.co.uk
Acked-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>