build: Allow bypassing the version checks

Introduce the CMake variable CHECK_TFM_TESTS_VERSION to allow not
performing the revision checks.
This is needed for TF-M forks where the upstream tags are not found,
which makes the build fail.

Change-Id: I3b5a22bb9ec609bf2ac097bf4803c10b14bf4f8e
Signed-off-by: Tomi Fontanilles <tomi.fontanilles@nordicsemi.no>