fsl_diu_fb.c: fix build warnings

Commit 15351855 "fsl-diu: Using I/O accessor to CCSR space" caused a
number of "passing argument 2 of 'out_be32' makes integer from pointer
without a cast" warnings; fix these.

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