powerpc: Remaining 64-bit Book3E support

This contains all the bits that didn't fit in previous patches :-) This
includes the actual exception handlers assembly, the changes to the
kernel entry, other misc bits and wiring it all up in Kconfig.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/xmon/xmon.c

@@ -2570,7 +2570,7 @@ static void xmon_print_symbol(unsigned long address, const char *mid,
 	printf("%s", after);
 }
 
-#ifdef CONFIG_PPC64
+#ifdef CONFIG_PPC_BOOK3S_64
 static void dump_slb(void)
 {
 	int i;