powerpc: minor cleanups for mpc86xx

* Remove duplicated cputable entry for 8641 (matches w/7448)
* Removed __init from function prototypes in mpc86xx.h
* Moved pci fixups into board specific code
* Moved mpc86xx_exclude_device to generic mpc86xx pci code
* Fixed sparse warnings in mpc86xx_smp.c
* Removed board specific header include from asm-powerpc/mpc86xx.h

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>