drm/amdkfd: only flush the validate MES contex

The following page fault was observed duringthe KFD process release.
In this particular error case, the HIP test (./MemcpyPerformance -h)
does not require the queue. As a result, the process_context_addr was
not assigned when the KFD process was released, ultimately leading to
this page fault during the execution of the function
kfd_process_dequeue_from_all_devices().

[345962.294891] amdgpu 0000:03:00.0: amdgpu: [gfxhub] page fault (src_id:0 ring:153 vmid:0 pasid:0)
[345962.295333] amdgpu 0000:03:00.0: amdgpu:   in page starting at address 0x0000000000000000 from client 10
[345962.295775] amdgpu 0000:03:00.0: amdgpu: GCVM_L2_PROTECTION_FAULT_STATUS:0x00000B33
[345962.296097] amdgpu 0000:03:00.0: amdgpu:     Faulty UTCL2 client ID: CPC (0x5)
[345962.296394] amdgpu 0000:03:00.0: amdgpu:     MORE_FAULTS: 0x1
[345962.296633] amdgpu 0000:03:00.0: amdgpu:     WALKER_ERROR: 0x1
[345962.296876] amdgpu 0000:03:00.0: amdgpu:     PERMISSION_FAULTS: 0x3
[345962.297135] amdgpu 0000:03:00.0: amdgpu:     MAPPING_ERROR: 0x1
[345962.297377] amdgpu 0000:03:00.0: amdgpu:     RW: 0x0
[345962.297682] amdgpu 0000:03:00.0: amdgpu: [gfxhub] page fault (src_id:0 ring:169 vmid:0 pasid:0)

Signed-off-by: Prike Liang <Prike.Liang@amd.com>
Reviewed-by: Jonathan Kim <jonathan.kim@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org