drm/amdkfd: workaround address watch clearing bug for gfx v9.4.2

KFD currently relies on MEC FW to clear tcp watch control
register on UNMAP_PROCESS, but FW doesn't work on it,
which is a bug. So the solution is to clear the register
as gfx v9 in KFD.

Signed-off-by: Eric Huang <jinhuieric.huang@amd.com>
Reviewed-by: Jonathan Kim <jonathan.kim@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>