powerpc/85xx: use CONFIG_SYS_FSL_PCIE_COMPAT macro when setting the PCI LIODNs

The SET_PCI_LIODN() macro takes a compatible property string as a parameter, so that it knows
which PCI device tree node to look for.  The calls to these macros are using a hard-coded string,
but we already have the CONFIG_SYS_FSL_PCIE_COMPAT macro which contains the same string, so we
should use that.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>