m68k: move to a single instance of free_initmem()

Currently each sub-architecture has its own implementation if init_freemem().
There is two different cases that the various implementations deal with.
They either free the init memory, or they don't. We only need a single instance
to cover all cases.

The non-MMU version did some page alignment twidling, but this is not
neccessary. The current linker script enforces page alignment. It also
checked for CONFIG_RAMKERNEL, but this also is not necessary, the linker
script always keeps the init sections in RAM.

The MMU ColdFire version of free_initmem() was empty. There is no reason it
can't carry out the freeing of the init memory. So it is now changed and
tested to do this.

For the other MMU cases the code is the same. For the general Motorola MMU
case we free the init memory. For the SUN3 case we do nothing (though I
think it could safely free the init memory as well).

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