[PATCH] libata: Setup nbytes in ata_sg_init_one

Setup nbytes in ata_sg_init_one to the total transfer length
of the command. This is needed by some HBAs that need to know
the total transfer length of each command.

Signed-off-by: Brian King <brking@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>