drm/amdgpu/pm: Fix the error of pwm1_enable setting

Fix the pwm_mode value error which used for
pwm1_enable setting

Signed-off-by: Ma Jun <Jun.Ma2@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org