drm/amdgpu/mes: only invalid/prime icache when finish loading both pipe MES FWs.

invalid/prime icahce operation takes effect both pipes cuconrrently,
therefore CP_MES_IC_BASE_LO/HI and CP_MES_MDBASE_LO/HI both have to be
set before prime icache. Otherwise MES hardware gets garbage data in
above regsters and causes page fault

[  470.873200] amdgpu 0000:33:00.0: amdgpu: [gfxhub] page fault (src_id:0 ring:217 vmid:0 pasid:0, for process  pid 0 thread  pid 0)
[  470.873222] amdgpu 0000:33:00.0: amdgpu:   in page starting at address 0x000092cb89b00000 from client 10
[  470.873234] amdgpu 0000:33:00.0: amdgpu: GCVM_L2_PROTECTION_FAULT_STATUS:0x00000BB3
[  470.873242] amdgpu 0000:33:00.0: amdgpu:      Faulty UTCL2 client ID: CPC (0x5)
[  470.873247] amdgpu 0000:33:00.0: amdgpu:      MORE_FAULTS: 0x1
[  470.873251] amdgpu 0000:33:00.0: amdgpu:      WALKER_ERROR: 0x1
[  470.873256] amdgpu 0000:33:00.0: amdgpu:      PERMISSION_FAULTS: 0xb
[  470.873260] amdgpu 0000:33:00.0: amdgpu:      MAPPING_ERROR: 0x1
[  470.873264] amdgpu 0000:33:00.0: amdgpu:      RW: 0x0

Signed-off-by: Yifan Zhang <yifan1.zhang@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Tim Huang <Tim.Huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>