drm/amd/powerplay: remove set but not used variable 'threshold', 'state'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/gpu/drm/amd/powerplay/smumgr/fiji_smumgr.c: In function fiji_populate_single_graphic_level:
drivers/gpu/drm/amd/powerplay/smumgr/fiji_smumgr.c:943:11: warning: variable threshold set but not used [-Wunused-but-set-variable]
drivers/gpu/drm/amd/powerplay/smumgr/fiji_smumgr.c: In function fiji_populate_memory_timing_parameters:
drivers/gpu/drm/amd/powerplay/smumgr/fiji_smumgr.c:1504:8: warning: variable state set but not used [-Wunused-but-set-variable]

They are introduced by commit 2e112b4a ("drm/amd/pp:
remove fiji_smc/smumgr split."), but never used,
so remove it.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>