Update Trusty related makefiles for new build system.

  - No need to declare MODULE_USER anymore.
  - Reset local variables to make it possible to include this module
    more then once.
  - Use GLOBAL_DEFINES instead of GLOBAL_CFLAGS to set OPENSSL_SYS_TRUSTY

Change-Id: Ie4a2a234c45b5f5092c251b1276d11d355a2338d