Remove superfluous OpenSSL include paths.

The libcrypto and libssl modules (and their respective static and host
versions) use LOCAL_EXPORT_C_INCLUDE_DIRS thus just including the module
is sufficient.

Change-Id: I5f16c672aa4924d323e0472afdda9fad30d708a6
diff --git a/Android.mk b/Android.mk
index d06f4a1..236ab12 100644
--- a/Android.mk
+++ b/Android.mk
@@ -10,7 +10,6 @@
 LOCAL_CFLAGS := -DWITHOUT_IFADDRS -Wno-sign-compare
 LOCAL_SRC_FILES := ping6.c ping_common.c
 LOCAL_MODULE := ping6
-LOCAL_C_INCLUDES := external/openssl/include
 LOCAL_SHARED_LIBRARIES := libcrypto
 include $(BUILD_EXECUTABLE)