drm/amd/display: increase max link count and fix link->enc NULL pointer access

In the Linux kernel, the following vulnerability has been resolved: drm/amd/display: increase max link count and fix link->enc NULL pointer access [why] 1.) dc->links[MAX_LINKS] array size smaller than actual requested. max_connector + max_dpia + 4 virtual = 14. increase from 12 to 14. 2.) hw_init() access null LINK_ENC for dpia non display_endpoint. (cherry picked from commit d7f5a61e1b04ed87b008c8d327649d184dc5bb45)