eal: fix devargs leak on multi-process detach request

eal: fix devargs leak on multi-process detach request

Device detach triggered through IPC leaked some memory.
It allocated a devargs objects just to use it for
parsing the devargs string in order to retrieve the
device name. Those devargs weren't passed anywhere
and were never freed.

First of all, let's put those devargs on the stack,
so they doesn't need to be freed. Then free the
additional arguments string as soon as it's allocated,
because we won't need it.

Fixes: ac9e4a17370f ("eal: support attach/detach shared device from secondary")

Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
Acked-by: Qi Zhang <qi.z.zhang@intel.com>