drm/amdgpu: use true, false for bool variable in amdgpu_psp.c

Fixes coccicheck warning:

drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c:674:2-26: WARNING: Assignment of 0/1 to bool variable
drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c:794:1-25: WARNING: Assignment of 0/1 to bool variable
drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c:897:2-36: WARNING: Assignment of 0/1 to bool variable
drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c:1016:1-35: WARNING: Assignment of 0/1 to bool variable
drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c:1087:2-34: WARNING: Assignment of 0/1 to bool variable
drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c:1177:1-33: WARNING: Assignment of 0/1 to bool variable

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