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 am: a3f5202285 am: 313845f54b
am: 726bb5ead1

Change-Id: I5b53644472dcb14c94a339d122d1daa4c1e83729