m68knommu: remove obsolete 68360 support

Remove the obsolete Motorola/Freescale 68360 SoC support. It has been
bit rotting for many years with little active use in mainlne. There has
been no serial driver support for many years, so it is largely not
useful in its current state.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>