m68k: merge the init_task code for mmu and non-mmu targets

The init_task code can be the same for both mmu and non-mmu targets.
None of the alignment carried out in the the current init_task code
is necessary. The linker script takes care of aligning the init_thread
structure to a THREAD SIZE boundary, and that is all we need.

So use the init_task.c code for all target types, that makes m68k
code consistent with what most other architectures do.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>