mlxsw: spectrum_router_xm: Introduce basic XM cache flushing

Upon route insertion and removal, it is needed to flush possibly cached
entries from the XM cache. Extend XM op context to carry information
needed for the flush. Implement the flush in delayed work since for HW
design reasons there is a need to wait 50usec before the flush can be
done. If during this time comes the same flush request, consolidate it
to the first one. Implement this queued flushes by a hashtable.

v2:
* Fix GENMASK() high bit

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>