m68k,nommu: fix implicit cast from __user in __{get,put}_user_asm()

The assembly for __get_user_asm() & __put_user_asm() uses memcpy()
when the size is 8.

However, the pointer is always a __user one while memcpy() expects
a plain one and so this cast creates a lot of warnings when using
Sparse.

So, fix this by adding a cast to 'void __force *' at memcpy()'s
argument.

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>