Merge branch 'mlxsw-remove-xm-support'

Ido Schimmel says:

====================
mlxsw: Remove XM support

The XM was supposed to be an external device connected to the
Spectrum-{2,3} ASICs using dedicated Ethernet ports. Its purpose was to
increase the number of routes that can be offloaded to hardware. This was
achieved by having the ASIC act as a cache that refers cache misses to the
XM where the FIB is stored and LPM lookup is performed.

Testing was done over an emulator and dedicated setups in the lab, but
the product was discontinued before shipping to customers.

Therefore, in order to remove dead code and reduce complexity of the
code base, revert the three patchsets that added XM support.
====================

Link: https://lore.kernel.org/r/20220613132116.2021055-1-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>