common/cnxk: fix batch alloc completion poll logic

common/cnxk: fix batch alloc completion poll logic

The instruction generation was not correct due to
fact that volatile suppose to use with ccode variable
as well.

Change the logic to use gcc atomic builtin to
simplify and avoid explicit volatile from the code.

Fixes: 81af26789316 ("common/cnxk: support NPA batch alloc/free")
Cc: stable@dpdk.org
Signed-off-by: Jerin Jacob <jerinj@marvell.com>
Signed-off-by: Ashwin Sekhar T K <asekhar@marvell.com>