drm/i915/gvt: Missed to cancel dma map for ggtt entries

We have canceled dma map for ppgtt entries. Also we need to do it for
ggtt entries when them are invalidated.

This can fix task hung issue as:
[13517.791767] INFO: task gvt_service_thr:1081 blocked for more than 120 seconds.
[13517.792584] Not tainted 4.14.15+ #3
[13517.793417] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[13517.794267] gvt_service_thr D 0 1081 2 0x80000000
[13517.795132] Call Trace:
[13517.795996] ? __schedule+0x493/0x77b
[13517.796859] schedule+0x79/0x82
[13517.797740] schedule_preempt_disabled+0x5/0x6
[13517.798614] __mutex_lock.isra.0+0x2b5/0x445
[13517.799504] ? __switch_to_asm+0x24/0x60
[13517.800381] ? intel_gvt_cleanup+0x10/0x10
[13517.801261] ? intel_gvt_schedule+0x19/0x2b9
[13517.802107] intel_gvt_schedule+0x19/0x2b9
[13517.802954] ? intel_gvt_cleanup+0x10/0x10
[13517.803824] gvt_service_thread+0xe3/0x10d
[13517.804704] ? wait_woken+0x68/0x68
[13517.805588] kthread+0x118/0x120
[13517.806478] ? kthread_create_on_node+0x3a/0x3a
[13517.807381] ? call_usermodehelper_exec_async+0x113/0x11a
[13517.808307] ret_from_fork+0x35/0x40

v3: split out ggtt reset case.
v2: also unmap ggtt during reset.

Signed-off-by: Changbin Du <changbin.du@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>