libata: remove ATA_FLAG_{SRST|SATA_RESET}

These flags are marked as obsolete and the checks for them have been removed
by commit 29444088 (libata-sff: kill unused
ata_bus_reset()), so I think it's time to finally get rid of them...

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