[POWERPC] Fix undefined pmu_sys_suspended compilation error

pmu_sys_suspended is declared extern when:
	defined(CONFIG_PM_SLEEP) && defined(CONFIG_PPC32)
but only defined when:
	defined(CONFIG_SUSPEND) && defined(CONFIG_PPC32)
which is wrong.  Let's fix that.

Signed-off-by: Tony Breeds <tony@bakeyournoodle.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>