eal/memory: fix unused SIGBUS handler

eal/memory: fix unused SIGBUS handler

Since its introduction in 2018, the SIGBUS handler was never registered,
and all related functions were unused.

A SIGBUS can be received by the application when accessing to hugepages
even if mmap() was successful, This happens especially when running
inside containers when there is not enough hugepages. In this case, we
need to recover. A similar scheme can be found in eal_memory.c.

Fixes: 582bed1e1d1d ("mem: support mapping hugepages at runtime")
Cc: stable@dpdk.org
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>