Add Clang Asflags for mips

Like make, it needs -fPIC to be added to compile successfully.

Change-Id: I1d6f1388c42a84f331bbce1ecd669669441d986e
diff --git a/cc/mips_device.go b/cc/mips_device.go
index d88c906..cd92eab 100644
--- a/cc/mips_device.go
+++ b/cc/mips_device.go
@@ -211,6 +211,10 @@
 	return t.toolchainClangCflags
 }
 
+func (t *toolchainMips) ClangAsflags() string {
+	return "-fPIC"
+}
+
 func (t *toolchainMips) ClangCflags() string {
 	return t.clangCflags
 }