Remove bionic-specific ni_* workaround now bionic is cleaned up.

Bug: 9671560
Change-Id: I32abfc481fbd111c4d61a3d65da8821d2d2f9848
diff --git a/ping6_niquery.h b/ping6_niquery.h
index 85dd94c..fa6624a 100644
--- a/ping6_niquery.h
+++ b/ping6_niquery.h
@@ -2,19 +2,6 @@
 
 #define NI_NONCE_SIZE			8
 
-/* On Android, the ni_xxx macros are already provided by netinet/icmp6.h.
- * Undefine them here to avoid "ni_xxx redefined" compiler warnings. GCC
- * provides no way to suppress these except by completely disabling all
- * preprocessor warnings.
- */
-#ifdef ANDROID
-#undef ni_type
-#undef ni_code
-#undef ni_cksum
-#undef ni_qtype
-#undef ni_flags
-#endif
-
 /* Node Information Query */
 struct ni_hdr {
 	struct icmp6_hdr		ni_u;