powerpc/8xx: remove obsolete mgsuvd board

The MPC852 based mgsuvd board from Keymile was initially ported,
but later on not developed further. This patch removes the respective
files to decrease merging conflicts and unneeded maintenance.

Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
Acked-by: Heiko Schocher<hs@denx.de>
Cc: Vitaly Bordug <vitb@kernel.crashing.org>
Cc: Marcelo Tosatti <marcelo@kvack.org>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>