reset: simple: add BCM4908 MISC PCIe reset controller support

It's a trivial reset controller. One register with bit per PCIe core.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>