PCI: loongson: Use DECLARE_PCI_FIXUP_EARLY for bridge_class_quirk()

PCI: loongson: Use DECLARE_PCI_FIXUP_EARLY for bridge_class_quirk()

According to the datasheet of Loongson LS7A bridge chip, the old version
of Loongson LS7A PCIE port has a wrong value about PCI class which is
0x060000, the correct value should be 0x060400, this bug can be fixed by
"dev->class = PCI_CLASS_BRIDGE_PCI << 8;" at the software level and it
was fixed in hardware in the latest LS7A versions.

In order to maintain downward compatibility, use DECLARE_PCI_FIXUP_EARLY
instead of DECLARE_PCI_FIXUP_HEADER for bridge_class_quirk() to fix it as
early as possible.

Otherwise, in the function pci_setup_device(), the related code about
"dev->class" such as "class = dev->class >> 8;" and "dev->transparent
= ((dev->class & 0xff) == 1);" maybe get wrong value without EARLY fixup.

Link: https://lore.kernel.org/r/1595065176-460-1-git-send-email-yangtiezhu@loongson.cn
Fixes: 1f58cca5cf2b ("PCI: Add Loongson PCI Controller support")
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>