[POWERPC] Factor zImage's 44x reset code out of ebony.c

The ebony_exit() function which resets the Ebony board should in fact
be common to most if not all 44x boards.  This moves the function out
into 44x.c, renaming it, so it can be used by other 44x platforms.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/boot/ebony.c b/arch/powerpc/boot/ebony.c
index b1251ee..6349858 100644
--- a/arch/powerpc/boot/ebony.c
+++ b/arch/powerpc/boot/ebony.c
@@ -102,26 +102,10 @@
 	dt_fixup_mac_addresses(ebony_mac0, ebony_mac1);
 }
 
-#define SPRN_DBCR0		0x134
-#define   DBCR0_RST_SYSTEM	0x30000000
-
-static void ebony_exit(void)
-{
-	unsigned long tmp;
-
-	asm volatile (
-		"mfspr	%0,%1\n"
-		"oris	%0,%0,%2@h\n"
-		"mtspr	%1,%0"
-		: "=&r"(tmp) : "i"(SPRN_DBCR0), "i"(DBCR0_RST_SYSTEM)
-		);
-
-}
-
 void ebony_init(void *mac0, void *mac1)
 {
 	platform_ops.fixups = ebony_fixups;
-	platform_ops.exit = ebony_exit;
+	platform_ops.exit = ibm44x_dbcr_reset;
 	ebony_mac0 = mac0;
 	ebony_mac1 = mac1;
 	ft_init(_dtb_start, _dtb_end - _dtb_start, 32);