ppc4xx: Move 405EP pci code from cpu_init_f() to __pci_pre_init()

ppc4xx: Move 405EP pci code from cpu_init_f() to __pci_pre_init()

This patch moves some basic PCI initialisation from the 4xx cpu_init_f()
to cpu/ppc4xx/4xx_pci.c.

The original cpu_init_f() function enabled the 405EP's internal arbiter
in all situations. Also the HCE bit in cpc0_pci is always set.
The first is not really wanted for PCI adapter designs and the latter
is a general bug for PCI adapter U-Boots. Because it enables
PCI configuration by the system CPU even when the PCI configuration has
not been setup by the 405EP. The one and only correct place is
in pci_405gp_init() (see "Set HCE bit" comment).

So for compatibility reasons the arbiter is still enabled in any case,
but from weak pci_pre_init() so that it can be replaced by board specific
code.

Signed-off-by: Matthias Fuchs <matthias.fuchs@esd.eu>
Signed-off-by: Stefan Roese <sr@denx.de>