ppc/spapr: Use qemu_log_mask() for hcall_dprintf()

ppc/spapr: Use qemu_log_mask() for hcall_dprintf()

To see the output of the hcall_dprintf statements, you currently have
to enable the DEBUG_SPAPR_HCALLS macro in include/hw/ppc/spapr.h.
This is ugly because a) not every user who wants to debug guest
problems can or wants to recompile QEMU to be able to see such issues,
and b) since this macro is disabled by default, the code in the
hcall_dprintf() brackets tends to bitrot until somebody temporarily
enables that macro again.
Since the hcall_dprintf statements except one indicate guest
problems, let's always use qemu_log_mask(LOG_GUEST_ERROR, ...) for
this macro instead. One spot indicated an unimplemented host feature,
so this is changed into qemu_log_mask(LOG_UNIMP, ...) instead. Now
it's possible to see all those messages by simply adding the CLI
parameter "-d guest_errors,unimp", without the need to re-compile
the binary.

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