sim: ppc: fix some more Wunused-function warnings

When compiling with --enable-werror and CFLAGS="-O0 -g -Wall", we run into:
...
In file included from src/sim/ppc/cpu.h:26:0,
                 from src/sim/ppc/mon.c:25,
                 from src/sim/ppc/inline.c:64,
                 from idecode.c:26:
src/sim/ppc/device.h:788:8: error: 'device_event_queue_deschedule' \
  declared 'static' but never defined [-Werror=unused-function]
 (void) device_event_queue_deschedule
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...

This seems to be caused by the fact that the function is declared using
INLINE_EVENT instead of INLINE_DEVICE.

Fix this and a similar error in the same file.