Add ULP verification for fp32

Add a verifier to check two results are correct within a certain ULP
tolerance for IEEE-754 32-bit floating point values.

Add a test to check the ULP verifier is correct.

Signed-off-by: Jack Frankland <jack.frankland@arm.com>
Change-Id: Iaf43069f300999479d998e7837746b247ca5177e