examples: drop some conditionals checks from macros

examples: drop some conditionals checks from macros

We no longer need to worry about GCC version older than 7.4.0. The other
remaining conditionals checks were also overkill for the example code.
In the unlikely event that someone tries to re-use the code in a
scenario where further conditions apply they can figure out.

Reviewed-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>