BUG/MINOR: pools/buffers: make sure to always reserve the required buffers

BUG/MINOR: pools/buffers: make sure to always reserve the required buffers

Since recent commit ae07592 ("MEDIUM: pools: add CONFIG_HAP_NO_GLOBAL_POOLS
and CONFIG_HAP_GLOBAL_POOLS") the pre-allocation of all desired reserved
buffers was not done anymore on systems not using the shared cache. This
basically has no practical impact since these ones will quickly be refilled
by all the ones used at run time, but it may confuse someone checking if
they're allocated in "show pools".

That's only 2.4-dev, no backport is needed.