drm/radeon: Simplify bool comparison

Fix the following coccicheck warning:

./drivers/gpu/drm/radeon/rs690.c:190:6-35: WARNING: Comparison to bool.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/rs690.c

@@ -187,7 +187,7 @@ static void rs690_mc_init(struct radeon_device *rdev)
 		/* FastFB shall be used with UMA memory. Here it is simply disabled when sideport 
 		 * memory is present.
 		 */
-		if (rdev->mc.igp_sideport_enabled == false && radeon_fastfb == 1) {
+		if (!rdev->mc.igp_sideport_enabled && radeon_fastfb == 1) {
 			DRM_INFO("Direct mapping: aper base at 0x%llx, replaced by direct mapping base 0x%llx.\n", 
 					(unsigned long long)rdev->mc.aper_base, k8_addr);
 			rdev->mc.aper_base = (resource_size_t)k8_addr;