HNS redefined available in bits.h define and didn't use it, we can safely
delete it.

Link: https://lore.kernel.org/r/20191023054239.31648-1-leon@kernel.orgSigned-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>