ata: pata_it821x: Fix possible doc-rotted function names

Fixes the following W=1 kernel build warning(s):

drivers/ata/pata_it821x.c:346: warning: expecting prototype for it821x_passthru_dma_start(). Prototype was for it821x_passthru_bmdma_start() instead
drivers/ata/pata_it821x.c:369: warning: expecting prototype for it821x_passthru_dma_stop(). Prototype was for it821x_passthru_bmdma_stop() instead

Cc: Jens Axboe <[e-mail]>
Cc: Alan Cox <[e-mail]>
Cc: [e-mail]
Signed-off-by: Lee Jones <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jens Axboe <[e-mail]>

drivers/ata/pata_it821x.c

···
 }
 
 /**
- *	it821x_passthru_dma_start	-	DMA start callback
+ *	it821x_passthru_bmdma_start	-	DMA start callback
  *	@qc: Command in progress
  *
  *	Usually drivers set the DMA timing at the point the set_dmamode call
···
 }
 
 /**
- *	it821x_passthru_dma_stop	-	DMA stop callback
+ *	it821x_passthru_bmdma_stop	-	DMA stop callback
  *	@qc: ATA command
  *
  *	We loaded new timings in dma_start, as a result we need to restore