MFC r261896:

After r251709, avoid a clang 3.4 warning about an unused static const
variable (uma_max_ipers), when asserts are disabled.

Reviewed by:	glebius
MFC r261902:

In r260111, in sys/conf/files, I disabled warning about unused functions
for the wrong mcg.c, the one in ofed/drivers/infiniband/hw/mlx4.
Disable the warning for ofed/drivers/net/mlx4/mcg.c instead.
MFC r261903:

Disable warning about unused static const variables for sys/pci/ncr.c.