MIPS: add board qemu-mips64 support

Both big-endian and little-endian are tested with below commands:
Rom version: (Default, Now we config it as rom version)
qemu-system-mips64el -M mips -bios u-boot.bin -cpu MIPS64R2-generic -nographic
qemu-system-mips64 -M mips -bios u-boot.bin -cpu MIPS64R2-generic -nographic
Ram version:
qemu-system-mips64el -M mips -cpu MIPS64R2-generic -kernel u-boot -nographic
qemu-system-mips64 -M mips -cpu MIPS64R2-generic -kernel u-boot -nographic

Signed-off-by: Zhizhou Zhang <etou.zh@gmail.com>
Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/arch/mips/cpu/mips64/Makefile b/arch/mips/cpu/mips64/Makefile
new file mode 100644
index 0000000..be38664
--- /dev/null
+++ b/arch/mips/cpu/mips64/Makefile
@@ -0,0 +1,45 @@
+#
+# (C) Copyright 2003-2006
+# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
+#
+# See file CREDITS for list of people who contributed to this
+# project.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation; either version 2 of
+# the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+# MA 02111-1307 USA
+#
+
+include $(TOPDIR)/config.mk
+
+LIB	= $(obj)lib$(CPU).o
+
+START	= start.o
+COBJS-y	= cpu.o interrupts.o time.o cache.o
+
+SRCS	:= $(START:.o=.S) $(SOBJS-y:.o=.S) $(COBJS-y:.o=.c)
+OBJS	:= $(addprefix $(obj),$(SOBJS-y) $(COBJS-y))
+START	:= $(addprefix $(obj),$(START))
+
+all:	$(obj).depend $(START) $(LIB)
+
+$(LIB):	$(OBJS)
+	$(call cmd_link_o_target, $(OBJS))
+
+#########################################################################
+
+# defines $(obj).depend target
+include $(SRCTREE)/rules.mk
+
+sinclude $(obj).depend