drm/amdgpu: Change kiq initialize/reset sequence on gfx8

1. initialize kiq before initialize gfx ring.
2. set kiq ring ready immediately when kiq initialize
   successfully.
3. split function gfx_v8_0_kiq_resume into two functions.
   gfx_v8_0_kiq_resume is for kiq initialize.
   gfx_v8_0_kcq_resume is for kcq initialize.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>