drm/amdgpu: fix the warning about the expression (int)size - len

Converting size from size_t to int may overflow.
v2: keep reverse xmas tree order (Christian)
Signed-off-by: Jesse Zhang <jesse.zhang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -2065,12 +2065,13 @@ static ssize_t amdgpu_reset_dump_register_list_write(struct file *f,
 	struct amdgpu_device *adev = (struct amdgpu_device *)file_inode(f)->i_private;
 	char reg_offset[11];
 	uint32_t *new = NULL, *tmp = NULL;
-	int ret, i = 0, len = 0;
+	unsigned int len = 0;
+	int ret, i = 0;
 
 	do {
 		memset(reg_offset, 0, 11);
 		if (copy_from_user(reg_offset, buf + len,
-					min(10, ((int)size-len)))) {
+					min(10, (size-len)))) {
 			ret = -EFAULT;
 			goto error_free;
 		}