m68k: atari: Document data parameter of stdma_try_lock()

When building with W=1:

    arch/m68k/atari/stdma.c:69: warning: Function parameter or member 'data' not described in 'stdma_try_lock'

Fix this by documenting the data parameter.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/a69dd3ab0a224e40ce5ce7b30981e2d7a0285a83.1694613528.git.geert@linux-m68k.org

arch/m68k/atari/stdma.c

@@ -61,6 +61,7 @@ static irqreturn_t stdma_int (int irq, void *dummy);
 /**
  * stdma_try_lock - attempt to acquire ST DMA interrupt "lock"
  * @handler: interrupt handler to use after acquisition
+ * @data: cookie passed to the interrupt handler function
  *
  * Returns !0 if lock was acquired; otherwise 0.
  */