m68knommu: fix arg types for outs* functions

Compiling for any m68knommu targets will give the following warnings:

  CC      lib/iomap_copy.o
lib/iomap.c: In function ‘iowrite8_rep’:
lib/iomap.c:213:2: warning: passing argument 2 of ‘io_outsb’ discards qualifiers from pointer target type
arch/m68k/include/asm/io_no.h:58:20: note: expected ‘void *’ but argument is of type ‘const void *’
lib/iomap.c: In function ‘iowrite16_rep’:
lib/iomap.c:217:2: warning: passing argument 2 of ‘io_outsw’ discards qualifiers from pointer target type
arch/m68k/include/asm/io_no.h:66:20: note: expected ‘void *’ but argument is of type ‘const void *’
lib/iomap.c: In function ‘iowrite32_rep’:
lib/iomap.c:221:2: warning: passing argument 2 of ‘io_outsl’ discards qualifiers from pointer target type
arch/m68k/include/asm/io_no.h:74:20: note: expected ‘void *’ but argument is of type ‘const void *’

Fix it by puting in the appropriate const qualifier on the buf argument of
the m68knommu outs* inline functions.

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