[RAPIDIO] Change RIO function mpc85xx_ to fsl_

The driver is suitable for the Freescale MPC8641 processor as well as
85xx processors, so this changes the mpc85xx prefix to fsl.

Signed-off-by: Zhang Wei <wei.zhang@freescale.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>