m68k/q40: Undefine insl/outsl before redefining them

To use the PC parallel port driver on Q40, we need non-standard versions of
the insl/outsl accessors. Make sure to undefine them first, to kill this
compiler warning:

In file included from drivers/parport/parport_pc.c:67:
arch/m68k/include/asm/parport.h:14:1: warning: "insl" redefined
In file included from arch/m68k/include/asm/io.h:4,
                 from include/linux/scatterlist.h:10,
                 from include/linux/dma-mapping.h:9,
                 from drivers/parport/parport_pc.c:54:
arch/m68k/include/asm/io_mm.h:370:1: warning: this is the location of the previous definition
In file included from drivers/parport/parport_pc.c:67:
arch/m68k/include/asm/parport.h:15:1: warning: "outsl" redefined
In file included from arch/m68k/include/asm/io.h:4,
                 from include/linux/scatterlist.h:10,
                 from include/linux/dma-mapping.h:9,
                 from drivers/parport/parport_pc.c:54:
arch/m68k/include/asm/io_mm.h:373:1: warning: this is the location of the previous definition

Reported-by: Thorsten Glaser <tg@debian.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>