drm/amdgpu/debugfs: fix memory leak when amdgpu_virt_enable_access_debugfs failed

Fix memory leak in amdgpu_debugfs_gpr_read not freeing data when
amdgpu_virt_enable_access_debugfs failed.

Fixes: 95a2f91738 ("drm/amdgpu: restrict debugfs register access under SR-IOV")
Signed-off-by: Chen Tao <chentao107@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -941,7 +941,7 @@ static ssize_t amdgpu_debugfs_gpr_read(struct file *f, char __user *buf,
 
 	r = amdgpu_virt_enable_access_debugfs(adev);
 	if (r < 0)
-		return r;
+		goto err;
 
 	/* switch to the specific se/sh/cu */
 	mutex_lock(&adev->grbm_idx_mutex);