drm/amd/display: Increase array size of dummy_boolean

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.

Reviewed-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Jerry Zuo <jerry.zuo@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>