REFCLK1 has req/ack bits that need to be programmed, just like REFCLK0.

Link: https://lore.kernel.org/r/20211117140044.193865-1-marcan@marcan.st
Fixes: 1e33888f ("PCI: apple: Add initial hardware bring-up")
Signed-off-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>