amdgpu/pm: Prevent force of DCEFCLK on NAVI10 and SIENNA_CICHLID

Writing to dcefclk causes the gpu to become unresponsive, and requires a reboot.
Patch ignores a .force_clk_levels(SMU_DCEFCLK) call and issues an
info message.

Signed-off-by: Darren Powell <darren.powell@amd.com>
Reviewed-by: Kenneth Feng <kenneth.feng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>