powerpc/cputable: Move __cpu_setup() prototypes out of cputable.h

Move all prototypes out of cputable.h

For that rename cpu_setup_power.h to cpu_setup.h and move all
prototypes in it.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
[mpe: Standardise cpu_spec *spec formatting]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/f45118489ee450db654db8bbcdfd8f5907337c22.1663606875.git.christophe.leroy@csgroup.eu