ata_piix: Add MODULE_PARM_DESC to prefer_ms_hyperv

In reference to the commit cd006086
"ata_piix: defer disks to the Hyper-V drivers by default",
this trivial patch adds a description to prefer_ms_hyperv.

[rvrbovsk@redhat.com: MODULE_PARM_DESC() string formatting modified]
Signed-off-by: Andrew Brownfield <abrownfi@redhat.com>
Signed-off-by: Radomir Vrbovsky <rvrbovsk@redhat.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/ata_piix.c

@@ -1547,6 +1547,10 @@ static bool piix_broken_system_poweroff(struct pci_dev *pdev)
 
 static int prefer_ms_hyperv = 1;
 module_param(prefer_ms_hyperv, int, 0);
+MODULE_PARM_DESC(prefer_ms_hyperv,
+	"Prefer Hyper-V paravirtualization drivers instead of ATA, "
+	"0 - Use ATA drivers, "
+	"1 (Default) - Use the paravirtualization drivers.");
 
 static void piix_ignore_devices_quirk(struct ata_host *host)
 {