sata_via: restore vt*_prepare_host error handling

sata_via: restore vt*_prepare_host error handling

commit b9d5b89b487517cbd4cb4702da829e07ef9e4432 (sata_via: fix support
for 5287) accidently (?) removed vt*_prepare_host error handling - restore it

catched by gcc:
drivers/ata/sata_via.c: In function 'svia_init_one':
drivers/ata/sata_via.c:567: warning: 'host' may be used uninitialized in this function

Signed-off-by: Marcin Slusarz <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Joseph Chan <[email protected]>
Cc: Jeff Garzik <[email protected]>
Signed-off-by: Jeff Garzik <[email protected]>