[MIPS] Introduce _machine_restart

Handles machine specific functions by using weak functions.

Signed-off-by: Shinya Kuribayashi <skuribay@ruby.dti.ne.jp>
diff --git a/board/tb0229/tb0229.c b/board/tb0229/tb0229.c
index 61c2e9b..d08b422 100644
--- a/board/tb0229/tb0229.c
+++ b/board/tb0229/tb0229.c
@@ -12,10 +12,17 @@
 #include <common.h>
 #include <command.h>
 #include <asm/addrspace.h>
-#include <asm/inca-ip.h>
 #include <asm/io.h>
+#include <asm/reboot.h>
 #include <pci.h>
 
+void _machine_restart(void)
+{
+	void (*f)(void) = (void *) 0xbfc00000;
+
+	f();
+}
+
 #if defined(CONFIG_PCI)
 static struct pci_controller hose;