drm/amdgpu/powerplay: fix missing break in switch statements

[ Upstream commit 14b284832e7dea6f54f0adfd7bed105548b94e57 ]

There are several switch statements that are missing break statements.
Add missing breaks to handle any fall-throughs corner cases.

Detected by CoverityScan, CID#1457175 ("Missing break in switch")

Fixes: 18aafc59 ("drm/amd/powerplay: implement fw related smu interface for iceland.")
Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>