drm/amdgpu/soc15: initialize reg base for navi14 (v2)

Initialize the IP register base offsets for navi14.

v2: squash in MP, CLK, THM updates

Signed-off-by: Xiaojie Yuan <xiaojie.yuan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Jack Xiao <Jack.Xiao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>