tests/radeon: set the list* functions as inline

To silence the chatty compiler.
As a future work we may want to merge these with libdrm_lists.h

Cc: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Jan Vesely <jan.vesely@rutgers.edu>