Expose the MacAddress class in the api

Test: built,  flashed, $ runtest frameworks-net
Bug: 69390696
Change-Id: Ica5efdf5ffe8ad2500a87f574508a2bcd074b33d
Merged-In: Ica5efdf5ffe8ad2500a87f574508a2bcd074b33d

(cherry picked from commit d411cf61ed5b948aaf6f6234217d6c6999c35159)
diff --git a/core/java/android/net/MacAddress.java b/core/java/android/net/MacAddress.java
index 5620a62..3458861 100644
--- a/core/java/android/net/MacAddress.java
+++ b/core/java/android/net/MacAddress.java
@@ -33,8 +33,6 @@
  *
  * This class only supports 48 bits long addresses and does not support 64 bits long addresses.
  * Instances of this class are immutable.
- *
- * @hide
  */
 public final class MacAddress implements Parcelable {