drm/amdgpu: Replace DEFINE_SIMPLE_ATTRIBUTE with DEFINE_DEBUGFS_ATTRIBUTE

Fix the following coccicheck warning:
./drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c:1589:0-23: WARNING:
fops_ib_preempt should be defined with DEFINE_DEBUGFS_ATTRIBUTE
./drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c:1592:0-23: WARNING:
fops_sclk_set should be defined with DEFINE_DEBUGFS_ATTRIBUTE
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c

@@ -1532,10 +1532,10 @@ static int amdgpu_debugfs_sclk_set(void *data, u64 val)
 	return 0;
 }
 
-DEFINE_SIMPLE_ATTRIBUTE(fops_ib_preempt, NULL,
+DEFINE_DEBUGFS_ATTRIBUTE(fops_ib_preempt, NULL,
 			amdgpu_debugfs_ib_preempt, "%llu\n");
 
-DEFINE_SIMPLE_ATTRIBUTE(fops_sclk_set, NULL,
+DEFINE_DEBUGFS_ATTRIBUTE(fops_sclk_set, NULL,
 			amdgpu_debugfs_sclk_set, "%llu\n");
 
 int amdgpu_debugfs_init(struct amdgpu_device *adev)