[POWERPC] 8xx: Rename m8xx_pic_init to mpc8xx_pics_init

m8xx_pic_init calls both mpc8xx_pic_init and cpm_pic_init. Renaming the
function to use the same name space as the rest of the mpc8xx
specific funtions and to be more meaningful.

m8xx_pic_init is declared in ppc8xx_pic.h but defined nowhere in the ppc
tree. Remove it.

Signed-off-by: Jochen Friedrich <jochen@scram.de>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>