drm/i915: Bump timeout for wait_for_engines()

drm/i915: Bump timeout for wait_for_engines()

Extract the timeout we use in i915_gem_idle_work_handler() and reuse it
for wait_for_engines() in i915_gem_wait_for_idle(). It too has the same
problem in sometimes having to wait for an extended period before the HW
settles, so make use of the same timeout.

References: 5427f207852d ("drm/i915: Bump wait-times for the final CS interrupt before parking")
Signed-off-by: Chris Wilson <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: Mika Kuoppala <[email protected]>
Reviewed-by: Joonas Lahtinen <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]