m32r: define ioread* and iowrite* macros

Define ioread* and iowrite* macros to fix the following build errors:

  CC [M]  drivers/uio/uio_smx.o
drivers/uio/uio_smx.c: In function 'smx_handler':
drivers/uio/uio_smx.c:31: error: implicit declaration of function 'ioread32'
drivers/uio/uio_smx.c:37: error: implicit declaration of function 'iowrite32'

Signed-off-by: Hirokazu Takata <takata@linux-m32r.org>