ata: optimize struct ata_force_param size

Optimize struct ata_force_param size by:
- using u8 for cbl and spd_limit fields
- using u16 for lflags field

Code size savings on m68k arch using (modified) atari_defconfig:

   text    data     bss     dec     hex filename
before:
  41064     573      40   41677    a2cd drivers/ata/libata-core.o
after:
  40654     573      40   41267    a133 drivers/ata/libata-core.o

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/libata.h

@@ -174,6 +174,7 @@ enum {
 	ATA_DEV_NONE		= 11,	/* no device */
 
 	/* struct ata_link flags */
+	/* NOTE: struct ata_force_param currently stores lflags in u16 */
 	ATA_LFLAG_NO_HRST	= (1 << 1), /* avoid hardreset */
 	ATA_LFLAG_NO_SRST	= (1 << 2), /* avoid softreset */
 	ATA_LFLAG_ASSUME_ATA	= (1 << 3), /* assume ATA class */