drm/amd/display: Increase array size of dummy_boolean

In the Linux kernel, the following vulnerability has been resolved: drm/amd/display: Increase array size of dummy_boolean [WHY] dml2_core_shared_mode_support and dml_core_mode_support access the third element of dummy_boolean, i.e. hw_debug5 = &s->dummy_boolean[2], when dummy_boolean has size of 2. Any assignment to hw_debug5 causes an OVERRUN. [HOW] Increase dummy_boolean's array size to 3. This fixes 2 OVERRUN issues reported by Coverity.