drm/amd/display: Fix late derefrence 'dsc' check in 'link_set_dsc_pps_packet()'

In the Linux kernel, the following vulnerability has been resolved:

drm/amd/display: Fix late derefrence 'dsc' check in 'link_set_dsc_pps_packet()'

In link_set_dsc_pps_packet(), 'struct display_stream_compressor *dsc'

was dereferenced in a DC_LOGGER_INIT(dsc->ctx->logger); before the 'dsc'

NULL pointer check.

Fixes the below:

drivers/gpu/drm/amd/amdgpu/../display/dc/link/link_dpms.c:905 link_set_dsc_pps_packet() warn: variable dereferenced before check 'dsc' (see line 903)