More fixes for BoringSSL compilation.

EC_GROUP_set_point_conversion_form has been removed in BoringSSL because
it didn't do anything.

Also, BoringSSL uses size_t and keymaster builds with a signed/unsigned
mismatch as a fatal error. This means that the casts to int aren't
needed in BoringSSL and, in fact, cause an error.

Change-Id: I52b7d34a5c90f40cfcc84c60b746404f374b1e80
diff --git a/ecdsa_key.cpp b/ecdsa_key.cpp
index a9f4ba7..84d9649 100644
--- a/ecdsa_key.cpp
+++ b/ecdsa_key.cpp
@@ -49,8 +49,8 @@
         return NULL;
     }
 
-    EC_GROUP_set_point_conversion_form(group.get(), POINT_CONVERSION_UNCOMPRESSED);
 #if !defined(OPENSSL_IS_BORINGSSL)
+    EC_GROUP_set_point_conversion_form(group.get(), POINT_CONVERSION_UNCOMPRESSED);
     EC_GROUP_set_asn1_flag(group.get(), OPENSSL_EC_NAMED_CURVE);
 #endif