malloc: fix documentation of realloc function

malloc: fix documentation of realloc function

The documentation for rte_realloc claims that the resized area
will always reside on the same NUMA node. This is not actually
the case - while *resized* area will be on the same NUMA node,
if resizing the area is not possible, then the memory will be
reallocated using rte_malloc(), which can allocate memory on
another NUMA node, depending on which lcore rte_realloc() was
called from and which NUMA nodes have memory available.

Fix the API doc to match the actual code of rte_realloc().

Fixes: af75078fece3 ("first public release")
Cc: stable@dpdk.org
Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>