Add new KeyMint curve enum

Bug: 194358913
Test: VtsAidlKeyMintTargetTest
Change-Id: I6fb21c0662f2c810a086c5146fa3caa51be9464e
diff --git a/include/hardware/keymaster_defs.h b/include/hardware/keymaster_defs.h
index c0b3800..930aceb 100644
--- a/include/hardware/keymaster_defs.h
+++ b/include/hardware/keymaster_defs.h
@@ -304,6 +304,7 @@
     KM_EC_CURVE_P_256 = 1,
     KM_EC_CURVE_P_384 = 2,
     KM_EC_CURVE_P_521 = 3,
+    KM_EC_CURVE_CURVE_25519 = 4,
 } keymaster_ec_curve_t;
 
 /**