dma-buf: fence-chain: Document missing dma_fence_chain_init() parameter in kerneldoc

Fix W=1 compile warnings (invalid kerneldoc):

drivers/dma-buf/dma-fence-chain.c:233: warning: Function parameter or member 'seqno' not described in 'dma_fence_chain_init'

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Sumit Semwal <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/dma-buf/dma-fence-chain.c

···
  * @chain: the chain node to initialize
  * @prev: the previous fence
  * @fence: the current fence
+ * @seqno: the sequence number to use for the fence chain
  *
  * Initialize a new chain node and either start a new chain or add the node to
  * the existing chain of the previous fence.