i40e: added queue pair disable/enable functions

Add functions for queue pair enable/disable. Instead of resetting the
whole device, only the affected queue pair is disabled or enabled.

This plumbing is used in a later commit, when zero-copy AF_XDP support
is introduced.

Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>