ata: move sata_link_{debounce,resume}() to libata-sata.c

* move sata_link_{debounce,resume}() to libata-sata.c

* add static inline for CONFIG_SATA_HOST=n case (only one,
  for sata_link_resume() is needed)

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

   text    data     bss     dec     hex filename
before:
  32816     572      40   33428    8294 drivers/ata/libata-core.o
after:
  32724     572      40   33336    8238 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>