drm/amd/powerplay: Fix maybe-uninitialized in get_ppfeature_status

This fixes the warning below

error: ‘feature_mask’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
  *features_enabled = ((((uint64_t)feature_mask[0] << SMU_FEATURES_LOW_SHIFT) & SMU_FEATURES_LOW_MASK) |
                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
    (((uint64_t)feature_mask[1] << SMU_FEATURES_HIGH_SHIFT) & SMU_FEATURES_HIGH_MASK));
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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