drm/amd/display: Fix potential mem leak in DC construct

Found by smatch:
drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc.c:506 construct() warn:
possible memory leak of 'dc_ctx'
drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc.c:506 construct() warn:
possible memory leak of 'dc_vbios'
drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc.c:506 construct() warn:
possible memory leak of 'dcn_ip'
drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc.c:506 construct() warn:
possible memory leak of 'dcn_soc'

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>