Always use Fermat's Little Theorem in ecdsa_sign_setup. am: c5f118738a am: 424cd02670 am: f40f1ba20b am: 44720342df  -s ours am: 432b1ecc99 am: 60102fdb0b
am: c79b025b9a

Change-Id: Ia6a0eb705925f0e170451c48730b7188a7fb4c30