[RAPIDIO] Add RapidIO multi mport support

The original RapidIO driver suppose there is only one mpc85xx RIO controller
in system.  So, some data structures are defined as mpc85xx_rio global, such
as 'regs_win', 'dbell_ring', 'msg_tx_ring'.  Now, I changed them to mport's
private members.  And you can define multi RIO OF-nodes in dts file for multi
RapidIO controller in one processor, such as PCI/PCI-Ex host controllers in
Freescale's silicon.  And the mport operation function declaration should be
changed to know which RapidIO controller is target.

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>