Support incremental CL tuning
Support incremental CL tuning

Allow reading of an existing params file even when tuning.

Signed-off-by: Stuart Taylor <b3105356f7ad85729108f63cf6e998ee4af61159@arm.com>
Change-Id: I6c6d9ec60908d644afbb5ff1c55f4a6cacf650d2

ARM-software/armnn,ARM-software/armnn,ARM-software/armnn