powerpc: drop MPC832x_MDS platform support

powerpc: drop MPC832x_MDS platform support

This final variant in the e300 family of Modular Development System
(MDS) in this series was actually aimed at feature reduction - things
like floating point and ethernet were removed in order to make for a
lower power and lower cost system.

Like all the MDS systems, it was meant as a vehicle to get the CPU out
early to hardware OEMs so software and board development could take place
in parallel.

These were made in limited numbers and availability preference was given
to partners who were planning to make their own boards.

Given that the whole reason for existence was to assist in enabling new
board designs [not happening for 10+ years], and that they weren't
generally available, and that the hardware wasn't really hobbyist friendly
even for retro computing, it makes sense to retire the support for this
particular platform.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Acked-by: Li Yang <leoyang.li@nxp.com>
[mpe: Drop stale reference to MPC832x_MDS in arch/powerpc/boot/Makefile]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230220115913.25811-5-paul.gortmaker@windriver.com