powerpc/swiotlb: Enable at early stage and disable if not necessary

Remove the dependency on PCI initialization for SWIOTLB initialization.
So that PCI can be initialized at proper time.

SWIOTLB is partly determined by PCI inbound/outbound map which is assigned
in PCI initialization. But swiotlb_init() should be done at the stage of
mem_init() which is much earlier than PCI initialization. So we reserve the
memory for SWIOTLB first and free it if not necessary.

All boards are converted to fit this change.

Signed-off-by: Jia Hongtao <B38951@freescale.com>
Signed-off-by: Li Yang <leoli@freescale.com>
Acked-by: Tony Breeds <tony@bakeyournoodle.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

arch/powerpc/include/asm/swiotlb.h

@@ -22,4 +22,10 @@ int __init swiotlb_setup_bus_notifier(void);
 
 extern void pci_dma_dev_setup_swiotlb(struct pci_dev *pdev);
 
+#ifdef CONFIG_SWIOTLB
+void swiotlb_detect_4g(void);
+#else
+static inline void swiotlb_detect_4g(void) {}
+#endif
+
 #endif /* __ASM_SWIOTLB_H */