drm/amd/pm: Avoid overflow when sorting pp_feature list

drm/amd/pm: Avoid overflow when sorting pp_feature list

pp_features sorting uses int8_t sort_feature[] to store driver
feature enum indices. On newer ASICs the enum index can exceed 127,
causing signed overflow and silently dropping entries from the output.
Switch the array to int16_t so all enum indices are preserved.

Signed-off-by: Asad Kamal <asad.kamal@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>