Rename createSHA256Parameters to createSha256Parameters

Fixes the following lint warning:
Warning S1: Method names with acronyms should be getMtu() instead of
getMTU()

Bug: 66499222
Test: adb shell am instrument -w -e package \
com.android.server.locksettings.recoverablekeystore \
com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner

Change-Id: If9eb03e2a2a63fe02a2da4828bd0c5c8997078b9