PM / EM: Fix debugfs entry creation

recent changes in debugfs dont allow to create directories till fs_init
call level, but some cpu clock drivers populate OPP table in prior init
call levels, the energy model debugfs population called from the OPP
framework, before debugfs initialization. This breaks energy model
population in debugfs.

Fix it by not allowing energy model population prior to debugfs init call,
and populate debugfs entries, if power domains already created.

Change-Id: I2fb747b2c033fa83d362fea1ff815a628448b00f
Signed-off-by: Lingutla Chandrasekhar <quic_lingutla@quicinc.com>
Signed-off-by: Srinivasarao Pathipati <quic_spathi@quicinc.com>