sata_mv: use {platform|pci}_get_drvdata()

The driver uses dev_get_drvdata() to get to the driver data for the
platform and PCI devices, while the corresponding wrappers exists for
them -- in one case it even declares an otherwise unneeded variable
to do that.  Switch to using the {platform|pci}_get_drvdata() instead.

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>