PCI: mediatek: Fix class type for MT7622 to PCI_CLASS_BRIDGE_PCI

commit 101c92dc ("PCI: mediatek: Set up vendor ID and class
type for MT7622") erroneously set the class type for MT7622 to
PCI_CLASS_BRIDGE_HOST.

The PCIe controller of MT7622 integrates a Root Port that has type 1
configuration space header and related bridge windows.

The HW default value of this bridge's class type is invalid.

Fix its class type and set it to PCI_CLASS_BRIDGE_PCI to
match the hardware implementation.

Fixes: 101c92dc ("PCI: mediatek: Set up vendor ID and class type for MT7622")
Signed-off-by: Honghui Zhang <honghui.zhang@mediatek.com>
[lorenzo.pieralisi@arm.com: reworked the commit log]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Ryder Lee <ryder.lee@mediatek.com>