Change PCIE1&2 deciide logic on MPC8544DS board more readable

The IO port selection for MPC8544DS board:
 Port			cfg_io_ports
 PCIE1		0x2, 0x3, 0x4, 0x5, 0x6, 0x7
 PCIE2		0x4, 0x5, 0x6, 0x7
 PCIE3		0x6, 0x7
 This patch changes the PCIE12 and PCIE2 logic more readable.
Signed-off-by: Roy Zang <tie-fei.zang@freescale.com>