mem: refactor memzone reserve functions

mem: refactor memzone reserve functions

The definitions of rte_memzone_reserve_aligned() and
rte_memzone_reserve_bounded() were identical with the exception of the
bound argument passed into rte_memzone_reserve_thread_safe().

This patch removes this replication of code by unifying it into
rte_memzone_reserve_thread_safe(), which is then called by all three
variants of rte_memzone_reserve().

Signed-off-by: Cyril Chemparathy <cchemparathy@ezchip.com>
Signed-off-by: Zhigang Lu <zlu@ezchip.com>