powerpc/8xx: add __init to cpm1 init functions

Functions cpm1_clk_setup(), cpm1_set_pin(), cpm_pic_init() and
mpc8xx_pic_init() are only called from __init functions, so mark
them __init as well.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/c27168ef054f3a52edcf0ff91652700d53b3e32d.1568294563.git.christophe.leroy@c-s.fr