[MIPS] Make ioremap() work on TX39/49 special unmapped segment

TX39XX and TX49XX have "reserved" segment in CKSEG3 area.
0xff000000-0xff3fffff on TX49XX and 0xff000000-0xfffeffff on TX39XX
are reserved (unmapped, uncached).  Controllers on these SoCs are
placed in this segment.

This patch add plat_ioremap() and plat_iounmap() to override default
behavior and implement these hooks for TX39/TX49.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/include/asm-mips/io.h b/include/asm-mips/io.h
index 92ec261..12bcc1f 100644
--- a/include/asm-mips/io.h
+++ b/include/asm-mips/io.h
@@ -178,6 +178,11 @@
 static inline void __iomem * __ioremap_mode(phys_t offset, unsigned long size,
 	unsigned long flags)
 {
+	void __iomem *addr = plat_ioremap(offset, size, flags);
+
+	if (addr)
+		return addr;
+
 #define __IS_LOW512(addr) (!((phys_t)(addr) & (phys_t) ~0x1fffffffULL))
 
 	if (cpu_has_64bit_addresses) {
@@ -282,6 +287,9 @@
 
 static inline void iounmap(const volatile void __iomem *addr)
 {
+	if (plat_iounmap(addr))
+		return;
+
 #define __IS_KSEG1(addr) (((unsigned long)(addr) & ~0x1fffffffUL) == CKSEG1)
 
 	if (cpu_has_64bit_addresses ||