drm/amd/powerplay: initlialize smu->is_apu is false by default

the member of is_apu in smu_context need to initlialize by default.

set default value is false (dGPU)

for patch:
	drm/amd/powerplay: bypass dpm_context null pointer check guard
	for some smu series

Signed-off-by: Kevin Wang <kevin1.wang@amd.com>
Reviewed-by: Kenneth Feng <kenneth.feng@amd.com>
Reviewed-by: Prike Liang <Prike.Liang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>