MIPS: Netlogic: Specify architecture CFLAGS

Use -march=xlr if available, otherwise fallback to mips64. This allows
us to support compilation with MIPS toolchains which are not customized
for XLR.

[ralf@linux-mips.org: And more importantly it works around a gas bug in
binutils 2.21 which otherwise may result in an assertion failure building
arch/mips/kernel/genex.S.  See
http://sourceware.org/bugzilla/show_bug.cgi?id=12915 for details.]
Signed-off-by: NJayachandran C <jayachandranc@netlogicmicro.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2534/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/netlogic/Platform

@@ -4,6 +4,11 @@
 cflags-$(CONFIG_NLM_COMMON)  += -I$(srctree)/arch/mips/include/asm/mach-netlogic
 cflags-$(CONFIG_NLM_COMMON)  += -I$(srctree)/arch/mips/include/asm/netlogic
 
+#
+# use mips64 if xlr is not available
+#
+cflags-$(CONFIG_NLM_XLR)	+= $(call cc-option,-march=xlr,-march=mips64)
+
 #
 # NETLOGIC XLR/XLS SoC, Simulator and boards
 #