drm/amd/display: Remove brackets in macro to conform to coding style

[Why]
Many of the register macros defined ind dcn32_resource.h have
extra brackets. This is not conforming to the style of those
defined in other DC header files.

[How]
Remove these brackets in dcn32_resource.h
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Stylon Wang <stylon.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>