COMPMID-766 Allow graph examples to run without OpenCL being present on the platform

Change-Id: I4142e0720ecb58549a08d4e86ad21abb882f5f37
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/114552
Reviewed-by: Anthony Barbier <anthony.barbier@arm.com>
Tested-by: Anthony Barbier <anthony.barbier@arm.com>
4 files changed