Move SHA256_SIZE define to libnetdutils and stop including netd header

Bug: 135235267
Test: m
      cd system/netd && atest
Change-Id: Ibe1dc22a2f3b762f10475e135613a9030bbe28b4
diff --git a/libnetdutils/include/netdutils/NetworkConstants.h b/libnetdutils/include/netdutils/NetworkConstants.h
index 682ceaf..dead9a1 100644
--- a/libnetdutils/include/netdutils/NetworkConstants.h
+++ b/libnetdutils/include/netdutils/NetworkConstants.h
@@ -14,8 +14,7 @@
  * limitations under the License.
  */
 
-#ifndef NETDUTILS_NETWORKCONSTANTS_H_
-#define NETDUTILS_NETWORKCONSTANTS_H_
+#pragma once
 
 namespace android {
 namespace netdutils {
@@ -26,7 +25,8 @@
 constexpr int IPV6_ADDR_LEN = 16;
 constexpr int IPV6_ADDR_BITS = 128;
 
+// Referred from SHA256_DIGEST_LENGTH in boringssl
+constexpr size_t SHA256_SIZE = 32;
+
 }  // namespace netdutils
 }  // namespace android
-
-#endif  // NETDUTILS_NETWORKCONSTANTS_H_