libcxgb: export ppm release and tagmask set api

Export cxgbi_ppm_release() to release
ppod manager and cxgbi_tagmask_set() to
set tag mask, they are used by cxgb3i, cxgb4i
and cxgbit.

Signed-off-by: Varun Prakash <varun@chelsio.com>
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: David S. Miller <davem@davemloft.net>