drm/amd: remove possible condition with no effect (if == else)

This patch fix cocci warning:
drivers/gpu/drm/amd/display/dc/dcn314/dcn314_resource.c:1816:6-8:
WARNING: possible condition with no effect (if == else).

Signed-off-by: Bernard Zhao <bernard@vivo.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>