target/ppc: Use proper logging function for possible guest errors

target/ppc: Use proper logging function for possible guest errors

fprintf() and qemu_log_separate() are frowned upon these days for printing
logging information in QEMU. Accessing the wrong SPRs indicates wrong guest
behaviour in most cases, and we've got a proper way to log such situations,
which is the qemu_log_mask(LOG_GUEST_ERROR, ...) function. So use this
function now for logging the bad SPR accesses instead.

Signed-off-by: Thomas Huth <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Reviewed-by: Greg Kurz <[email protected]>
Reviewed-by: Alistair Francis <[email protected]>
Signed-off-by: David Gibson <[email protected]>