tc: keep only major version check

There is currently no reason to check for the patch level version of the
kernel, as we are trying to compare linux 5.15 with 6.1+. Updating
conditions everywhere.

In TF-A we check specifically for 6.6, or higher, so when we introduce
linux 7.0, the check there will need to be updated.

Signed-off-by: Alex Dobrescu <alex.dobrescu@arm.com>