[POWERPC] PMAC_APM_EMU should depend on ADB_PMU

This patch fixes undefined refereneces to pmu_ symbols on 2.6.17.

Signed-Off-By: Danny van Dyk <kugelfang@gentoo.org>
Signed-off-by: Daniel Drake <dsd@gentoo.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>