dm: pci: Skip setting VGA bridge bits if parent device is the host bus

dm: pci: Skip setting VGA bridge bits if parent device is the host bus

Commit bbbcb5262839 ("dm: pci: Enable VGA address forwarding on bridges")
sets the VGA bridge bits by checking pplat->class, but if the parent
device is the pci host bus device, it can be skipped. Moreover, it
shouldn't access the pplat because the parent has different plat data.

Without this fix, "pci enum" command cause a synchronous abort.

pci_auto_config_devices: start
PCI Autoconfig: Bus Memory region: [78000000-7fffffff],
		Physical Memory [78000000-7fffffffx]
PCI Autoconfig: Bus I/O region: [0-ffff],
		Physical Memory [77f00000-77f0ffffx]
pci_auto_config_devices: device pci_6:0.0
PCI Autoconfig: BAR 0, Mem, size=0x1000000, address=0x78000000 bus_lower=0x79000000

PCI Autoconfig: BAR 1, Mem, size=0x8000000, No room in resource, avail start=79000000 / size=8000000, need=8000000
PCI: Failed autoconfig bar 14

PCI Autoconfig: BAR 2, I/O, size=0x4, address=0x1000 bus_lower=0x1004

PCI Autoconfig: BAR 3, Mem, size=0x2000000, address=0x7a000000 bus_lower=0x7c000000

PCI Autoconfig: BAR 4, I/O, size=0x80, address=0x1080 bus_lower=0x1100

PCI Autoconfig: ROM, size=0x80000, address=0x7c000000 bus_lower=0x7c080000

"Synchronous Abort" handler, esr 0x96000006
elr: 00000000e002bd28 lr : 00000000e002bce8 (reloc)
elr: 00000000fff6fd28 lr : 00000000fff6fce8
x0 : 0000000000001041 x1 : 000000000000003e
x2 : 00000000ffb0f8c8 x3 : 0000000000000001
x4 : 0000000000000080 x5 : 0000000000000000
x6 : 00000000fff718fc x7 : 000000000000000f
x8 : 00000000ffb0f238 x9 : 0000000000000008
x10: 0000000000000000 x11: 0000000000000010
x12: 0000000000000006 x13: 000000000001869f
x14: 00000000ffb0fcd0 x15: 0000000000000020
x16: 00000000fff71cc4 x17: 0000000000000000
x18: 00000000ffb13d90 x19: 00000000ffb14320
x20: 0000000000000000 x21: 00000000ffb14090
x22: 00000000ffb0f8c8 x23: 0000000000000001
x24: 00000000ffb14c10 x25: 0000000000000000
x26: 0000000000000000 x27: 0000000000000000
x28: 00000000ffb14c70 x29: 00000000ffb0f830

Code: 52800843 52800061 52800e00 97ffcf65 (b9400280)
Resetting CPU ...

Signed-off-by: Masami Hiramatsu <masami.hiramatsu@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>