hw/ppc: Move ppc40x_*reset() functions from ppc405_uc.c to ppc.c

hw/ppc: Move ppc40x_*reset() functions from ppc405_uc.c to ppc.c

Currently, it is not possible to build a QEMU binary without the
ppc405_uc.c file, even if you do not want to have the embedded machines
in the binary. This is bad since it's quite a bit of code and this code
pulls in some more dependencies (e.g. via the usage of serial_mm_init())
which would not be needed otherwise - especially with the upcoming
Kconfig-style configuration system for QEMU.

The only functions from this file which are really always required for
linking are the ppc40x_*reset() functions, so move these functions to
ppc.c, close to the ppc40x_set_irq() function that calls them. Now we
can flag ppc405_uc.c and ppc4xx_devs.c with the CONFIG_PPC4XX config
switch, too.

And while we're at it, replace the printf()s in these ppc40x_*reset()
functions with proper calls to qemu_log_mask().

Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>