Export FrontendDvbtPlpMode

Test: make;
Change-Id: I3d4c0667ba1251b3038681759c50b453cd40a8ca
diff --git a/tv/tuner/1.0/types.hal b/tv/tuner/1.0/types.hal
index d39439d..8e36616 100644
--- a/tv/tuner/1.0/types.hal
+++ b/tv/tuner/1.0/types.hal
@@ -773,6 +773,7 @@
 /**
  *   Physical Layer Pipe (PLP) Mode for DVBT.
  */
+@export
 enum FrontendDvbtPlpMode : uint32_t {
     UNDEFINED,
     AUTO,