drm/amd/pm: bound pp_dpm_set_pp_table() memcpy

drm/amd/pm: bound pp_dpm_set_pp_table() memcpy

The powerplay path allocates hardcode_pp_table once with kmemdup(...,
soft_pp_table_size). memcpy(..., size) used the sysfs store count (up to
PAGE_SIZE) with no upper bound, causing heap overflow. Reject
writes where size exceeds soft_pp_table_size.

Signed-off-by: Asad Kamal <asad.kamal@amd.com>
Reviewed-by: Yang Wang <kevinyang.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>