[POWERPC] Uartlite: Revert register io access changes

Reverts commit a15da8eff3627b8368db7f5dd260e5643213d918

This driver is used by devices other than the xilinx opb-uartlite which
depend on bytewise access to the registers.  The change to 32 bit access
does not work on these devices.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>