Merge branch 'mlxsw-spectrum-prepare-for-xm-implementation-lpm-trees'

Ido Schimmel says:

====================
mlxsw: spectrum: Prepare for XM implementation - LPM trees

Jiri says:

This is a preparation patchset for follow-up support of boards with
extended mezzanine (XM), which are going to allow extended (scale-wise)
router offload.

XM requires a separate set of PRM registers to be used to configure LPM
trees. Therefore, this patchset introduces operations that allow
different implementations of tree configuration for legacy router
offload and the XM router offload.
====================

Link: https://lore.kernel.org/r/20201101134215.713708-1-idosch@idosch.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>