tests/amdgpu: Allow to exclude a test or a suite of tests

tests/amdgpu: Allow to exclude a test or a suite of tests

Add the command line argument -e s[.t] to exclude (disable) suite s, or to
exclude suite s test t.

This is useful for instance to run the Basic Suite, but disable the GPU reset
test, on the command line, like this:

    amdgpu_tests -s 1 -e 1.13

This option can be specified more than once on the command line, in order to
exclude more than one suite and/or suite and test combination from being run.

Cc: Alex Deucher <Alexander.Deucher@amd.com>
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>