test: lmb: Move tests into the lib suite

These tests are marked as driver model tests, but have nothing to do
with driver model. As a result, they are run as part of 'ut dm' which
only exists for sandbox.

Move them to the 'lib' suite and drop the requirement for initing
devices, since they don't use devices.

Also put the lib_test_lmb_max_regions() macro inside the same #ifdef
as its function, to avoid a build error if the condition is false.

Signed-off-by: Simon Glass <sjg@chromium.org>