Add Format_isValid() and Format_isEqual() to NBAIO

This is in preparation for changing the typedef to a struct.

Change-Id: I8eb1c7d98fd12f997641e462359864fdb834abe6
diff --git a/media/libnbaio/NBAIO.cpp b/media/libnbaio/NBAIO.cpp
index 8a8155d..cc12671 100644
--- a/media/libnbaio/NBAIO.cpp
+++ b/media/libnbaio/NBAIO.cpp
@@ -235,4 +235,14 @@
     return (ssize_t) NEGOTIATE;
 }
 
+bool Format_isValid(const NBAIO_Format& format)
+{
+    return format != Format_Invalid;
+}
+
+bool Format_isEqual(const NBAIO_Format& format1, const NBAIO_Format& format2)
+{
+    return format1 == format2;
+}
+
 }   // namespace android