sal: Rewrite digest tests to be simpler, enable them in check

Change-Id: I610e615be498237e5cd9dd963bca60c7f8f62aac
sal: Add rtl_digest_SHA1 which shows wrong sha1 calculation

This test shows wrong sha1 calculation after 52 bytes of input
data. For now this test is commented.

Change-Id: Id6df40ecc4059d4a4f9e1646a2c1bb7242f4cf69