MIPS: Loongson 2F: Enable fixups of the latest binutils

With the  "Fixups of Loongson2F" patch [1] having been applied to binutils
for binutils 2.20.1 we now can use it's time to enable the options provided
by the patch to compile the kernel.

Without these fixups, the system may hang if the erratum is triggered.

For more information on these fixups please refer to the following
references.

[1] "Fixups of Loongson2F" patch for binutils(actually for gas)
    http://sourceware.org/ml/binutils/2009-11/msg00387.html
[2] Chapter 15 of "Loongson2F User Manual"(Chinese Version)
    http://www.loongson.cn/uploadfile/file/200808211
[3] Chapter 15 of the English version Loongson 2F User Manual
    http://groups.google.com.hk/group/loongson-dev/msg/e0d2e220958f10a6?dmode=sourceSigned-off-by: NZhang Le <r0bertz@gentoo.org>
Signed-off-by: NWu Zhangjin <wuzhangjin@gmail.com>
Cc: Zhang Le <r0bertz@gentoo.org>
Cc: linux-mips <linux-mips@linux-mips.org>
Patchwork: http://patchwork.linux-mips.org/patch/1106/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/Makefile

@@ -136,6 +136,19 @@ cflags-$(CONFIG_CPU_LOONGSON2E) += \
 	$(call cc-option,-march=loongson2e,-march=r4600)
 cflags-$(CONFIG_CPU_LOONGSON2F) += \
 	$(call cc-option,-march=loongson2f,-march=r4600)
+# enable the workarounds for loongson2f
+ifdef CONFIG_CPU_LOONGSON2F_WORKAROUNDS
+  ifeq ($(call as-option,-Wa$(comma)-mfix-loongson2f-nop,),)
+    $(error only binutils >= 2.20.2 have needed option -mfix-loongson2f-nop)
+  else
+    cflags-$(CONFIG_CPU_NOP_WORKAROUNDS) += -Wa$(comma)-mfix-loongson2f-nop
+  endif
+  ifeq ($(call as-option,-Wa$(comma)-mfix-loongson2f-jump,),)
+    $(error only binutils >= 2.20.2 have needed option -mfix-loongson2f-jump)
+  else
+    cflags-$(CONFIG_CPU_JUMP_WORKAROUNDS) += -Wa$(comma)-mfix-loongson2f-jump
+  endif
+endif
 
 cflags-$(CONFIG_CPU_MIPS32_R1)	+= $(call cc-option,-march=mips32,-mips32 -U_MIPS_ISA -D_MIPS_ISA=_MIPS_ISA_MIPS32) \
 			-Wa,-mips32 -Wa,--trap