[POWERPC] Rename cpu_setup_power4.S to cpu_setup_ppc970.S

Rename cpu_setup_power4.S to cpu_setup_ppc970.S, since that's
really what it is.

No functional or other changes.

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>
2 files changed