pata_at91: call clk_put() on ata_host_activate() failure

pata_at91_probe() forgets to call clk_put() iff ata_host_activate() fails...

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