ata: move *sata_set_spd*() to libata-sata.c

ata: move *sata_set_spd*() to libata-sata.c

* move *sata_set_spd*() to libata-sata.c

* add static inlines for CONFIG_SATA_HOST=n case

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

   text    data     bss     dec     hex filename
before:
  32842     572      40   33458    82ae drivers/ata/libata-core.o
after:
  32812     572      40   33428    8290 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>