drm/amd/display: Simplify bool comparison

Fix the following coccicheck warning:
./drivers/gpu/drm/amd/display/dc/dcn10/dcn10_dpp_cm.c:580:23-31:
WARNING: Comparison to bool
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <abaci-bugfix@linux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_dpp_cm.c

@@ -577,7 +577,7 @@ void dpp1_power_on_degamma_lut(
 	struct dcn10_dpp *dpp = TO_DCN10_DPP(dpp_base);
 
 	REG_SET(CM_MEM_PWR_CTRL, 0,
-			SHARED_MEM_PWR_DIS, power_on == true ? 0:1);
+			SHARED_MEM_PWR_DIS, power_on ? 0:1);
 
 }