[MIPS] Disabled madd support for Ingenic Xburst CPUs.

1. Added xburst ARCH_VARIANT file 'mips32r2-fp-xburst.mk'.
   a) Added -mno-fused-madd GCC option.

2. Removing -mno-fused-madd GCC option for LLVM.


Change-Id: I947a74eb89c05ae321417533c3c40241abc6f965
Signed-off-by: Pete Delaney <piet.delaney@imgtec.com>
diff --git a/core/llvm_config.mk b/core/llvm_config.mk
index 7a26842..9fe392f 100644
--- a/core/llvm_config.mk
+++ b/core/llvm_config.mk
@@ -60,7 +60,8 @@
     -mtune=mips32r2 \
     -march=mips32 \
     -mtune=mips32 \
-    -msynci
+    -msynci \
+    -mno-fused-madd
 endif
 ifeq ($(TARGET_ARCH),x86)
   CLANG_CONFIG_EXTRA_CFLAGS += \