[opentitanlib] Add OTP hex file generation.

Signed-off-by: Jon Flatley <jflat@google.com>
diff --git a/sw/host/opentitanlib/src/lib.rs b/sw/host/opentitanlib/src/lib.rs
index 38e9c55..71ddeab 100644
--- a/sw/host/opentitanlib/src/lib.rs
+++ b/sw/host/opentitanlib/src/lib.rs
@@ -5,6 +5,7 @@
 pub mod app;
 pub mod bootstrap;
 pub mod io;
+pub mod otp;
 pub mod spiflash;
 pub mod transport;
 pub mod util;