PCI: brcmstb: Assert fundamental reset on initialization

commit 22e21e51 upstream.

While preparing the driver for upstream this detail was missed.

If not asserted during the initialization process, devices connected on
the bus will not be made aware of the internal reset happening. This,
potentially resulting in unexpected behavior.

Link: https://lore.kernel.org/r/20200507172020.18000-1-nsaenzjulienne@suse.de
Fixes: c0452137

 ("PCI: brcmstb: Add Broadcom STB PCIe host controller driver")
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>