Correct TuningLevel enumeration values

Correct TuningLevel enumeration values

According to the header description - include/armnn/IRuntime.hpp, Each level should have below value.
-----------------------------------------------------------------------------------------------------
"TuningLevel" : int [0..3] (0=UseOnly(default) | 1=RapidTuning | 2=NormalTuning | 3=ExhaustiveTuning)
-----------------------------------------------------------------------------------------------------

And also src/backends/cl/ClBackendContext.cpp uses below enumeration values internally
for the tuning level,
----------------------
enum class TuningLevel
{
    None,
    Rapid,
    Normal,
    Exhaustive
};
----------------------

So this patch corrects TuningLevel enumeration values - which is exposed to user - to be consistent
with ones internally used.

This is upstream patch,
	 https://review.mlplatform.org/c/ml/armnn/+/5269

Change-Id: I9a8aeea0115579bfd16cbe01f39183b96329cdfd
Signed-off-by: Inki Dae <inki.dae@samsung.com>