drm/amd/display: Fix out-of-bound accesses

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

drm/amd/display: Fix out-of-bound accesses

[WHAT & HOW]

hpo_stream_to_link_encoder_mapping has size MAX_HPO_DP2_ENCODERS(=4),

but location can have size up to 6. As a result, it is necessary to

check location against MAX_HPO_DP2_ENCODERS.

Similiarly, disp_cfg_stream_location can be used as an array index which

should be 0..5, so the ASSERT's conditions should be less without equal.