drm/amd/swsmu: add smu14 driver if file

Add initial smu14 driver if file

v2: squash in updates (Alex)
v3: squash in updates (Alex)
v4: squash in updates (Alex)

Signed-off-by: Kenneth Feng <kenneth.feng@amd.com>
Reviewed-by: Likun Gao <Likun.Gao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: Kenneth Feng