mlxsw: reg: Add Router LPM Cache ML Delete Register

The RLCMLD register is used to bulk delete the XLT-LPM cache ML entries.
This can be used by SW when L is increased or decreased, thus need to
remove entries with old ML values.

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