drm/amdgpu: Fix warnings

Fix below warning due to incompatible types in conditional operator

../pm/swsmu/smu13/smu_v13_0_6_ppt.c:315:17: sparse: sparse: incompatible
types in conditional expression (different base types):

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>
Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Link: https://lore.kernel.org/oe-kbuild-all/202303082135.NjdX1Bij-lkp@intel.com/


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