fsl-diu: Using I/O accessor to CCSR space

Using PPC I/O accessor to DIU I/O space instead of directly
read/write. It will prevent the dozen of compiler order issue
and PPC hardware order issue for accessing I/O space.

Using the toolchain(tc-fsl-x86lnx-e500-dp-4.3.74-2.i386.rpm)
can show up the order issue of DIU driver.

Signed-off-by: Dave Liu <daveliu@freescale.com>
Signed-off-by: Jerry Huang <Chang-Ming.Huang@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>